18.8: Detailed Figure Descriptions

Chapter Cover Image: Conceptual Model of Water Flow

The image is a detailed conceptual model illustrating the interactions between various components of the water management system. In the foreground, we see a cross-section of the land showing different layers of soil and rock. The top layer includes areas of irrigated agriculture, a recharge basin, and a wildlife refuge. A diversion canal redirects river water towards these agricultural fields and recharge areas.

Below the surface, the groundwater table is depicted, showing how water infiltrates through the soil to replenish both confined and unconfined aquifers. The confined aquifer is separated by an aquitard, a less permeable layer that restricts water flow.

On the right side, the image shows municipal and industrial supply wells drawing water from these aquifers for human use. Injection wells are also depicted, which are used to recharge the aquifer artificially.

In the background, mountains receive precipitation, which contributes to runoff flowing into streams and reservoirs. This water is directed through treatment plants before being supplied for municipal and industrial uses.

The left side of the image illustrates the river flowing towards the ocean, passing through various ecosystems, including areas with phreatophytes, plants that draw water from the water table. There is also a depiction of the salinity gradient as the river water meets the ocean.

Overall, the image captures the complex interactions and flow of water through natural and managed systems, highlighting the importance of each component in maintaining the water cycle and supporting various uses.

Figure 18.1.1: Water Cycle

The water cycle describes where water is found on Earth and how it moves. Water can be stored in the atmosphere, on Earth’s surface, or below the ground. It can be in a liquid, solid, or gaseous state. Water moves between the places it is stored at large scales and at very small scales. Water moves naturally and because of human interaction, both of which affect where water is stored, how it moves, and how clean it is. 

Liquid water can be fresh, saline (salty), or a mix (brackish). Ninety-six percent of all water is saline and stored in oceans. Places like the ocean, where water is stored, are called pools. On land, saline water is stored in saline lakes, whereas fresh water is stored in liquid form in freshwater lakes, artificial reservoirs, rivers, wetlands, and in soil as soil moisture. Deeper underground, liquid water is stored as groundwater in aquifers, within the cracks and pores of rock. The solid, frozen form of water is stored in ice sheets, glaciers, and snowpack at high elevations or near the Earth’s poles. Frozen water is also found in the soil as permafrost. Water vapor, the gaseous form of water, is stored as atmospheric moisture over the ocean and land. 

As it moves, water can transform into a liquid, a solid, or a gas. The different ways in which water moves between pools are known as fluxes. Circulation mixes water in the oceans and transports water vapor in the atmosphere. Water moves between the atmosphere and the Earth’s surface through evaporation, evapotranspiration, and precipitation. Water moves across the land surface through snowmelt, runoff, and streamflow. Through infiltration and groundwater recharge, water moves into the ground. When underground, groundwater flows within aquifers and can return to the surface through springs or from natural groundwater discharge into rivers and oceans.

Humans alter the water cycle. We redirect rivers, build dams to store water, and drain water from wetlands for development. We use water from rivers, lakes, reservoirs, and groundwater aquifers. We use that water (1) to supply our homes and communities; (2) for agricultural irrigation and grazing livestock; and (3) in industrial activities like thermoelectric power generation, mining, and aquaculture. The amount of available water depends on how much water is in each pool (water quantity). Water availability also depends on when and how fast water moves (water timing), how much water is used (water use), and how clean the water is (water quality). 

Human activities affect water quality. In agricultural and urban areas, irrigation and precipitation wash fertilizers and pesticides into rivers and groundwater. Power plants and factories return heated and contaminated water to rivers. Runoff carries chemicals, sediment, and sewage into rivers and lakes. Downstream from these types of sources, contaminated water can cause harmful algal blooms, spread diseases, and harm habitats. Climate change is also affecting the water cycle. It affects water quality, quantity, timing, and use. Climate change is also causing ocean acidification, sea level rise, and extreme weather. Understanding these impacts can allow progress toward sustainable water use.

Figure 18.1.2: Water Cycle Diagram by the United States Geological Survey

This image is a comprehensive diagram illustrating the water cycle, provided by the U.S. Geological Survey (USGS). The diagram details the various processes and pathways through which water moves on, above, and below the Earth's surface.

At the top left, the Sun is depicted, showing its role in driving evaporation from the ocean's surface. This process is labeled "ocean evaporation," and the water vapor rises into the atmosphere, forming "atmospheric moisture over the ocean." The diagram also illustrates the "transport of moisture from ocean to land," showing how water vapor moves over land where it precipitates as rain or snow, labeled "precipitation over land."

The land area includes various features where water is stored and flows. Snowpack and ice sheets at higher elevations store water as ice, which melts to contribute to rivers and streams, a process called "snowmelt." Rivers and streams transport water, some of which infiltrates the ground to recharge groundwater, depicted as "groundwater recharge." Surface runoff from precipitation flows into rivers, lakes, and wetlands, labeled as "runoff."

Several types of water bodies are shown, including freshwater lakes, saline lakes, rivers, and wetlands (both fresh and brackish). The diagram also shows human influences on the water cycle, such as "domestic water use," "municipal water use," "industrial water use," "agricultural water use," and "grazing water use." Urban runoff and streamflow to oceans illustrate how water returns to the ocean, completing the cycle.

The interaction between surface water and groundwater is highlighted with "groundwater storage," "soil moisture," and "groundwater discharge to ocean." The subsurface section of the diagram shows detailed layers of groundwater flow, indicating how water moves through aquifers and returns to the surface through springs or wells.

The diagram emphasizes various processes like "evapotranspiration," where water is transferred from land and plants back into the atmosphere, and "precipitation over land," contributing to rivers and groundwater. Other processes include "ocean circulation," which distributes water globally, and "groundwater discharge to rivers and oceans."

The diagram includes a legend explaining the different pools and fluxes involved in the water cycle, noting that pools are places where water is stored (such as lakes, rivers, and aquifers), and fluxes are ways water moves between pools (such as evaporation, precipitation, and runoff). A detailed description at the bottom provides additional context about how the water cycle functions and its importance to Earth's systems.

This diagram provides a detailed and informative overview of the water cycle, highlighting the complex interactions between different components of the Earth's hydrological system and the impact of human activities on water movement and storage.

Figure 18.2.1: Average Annual Precipitation for California 1900-1960

The image is a color-coded map of California displaying the average annual precipitation from 1900 to 1960. The title of the map is "Average Annual Precipitation of California 1900-1960." The data sources include the US Geological Survey, California Department of Water Resources, and California Division of Mines.

The map uses a gradient color scale to represent different precipitation levels. Dark blue indicates the highest precipitation levels, ranging from 51 to 125 inches annually. Light blue represents moderately high precipitation levels, ranging from 31 to 50 inches. Green signifies mid-range precipitation levels, from 21 to 30 inches. Yellow shows lower precipitation levels, ranging from 11 to 20 inches. Orange and red indicate the lowest precipitation levels, ranging from 3 to 10 inches.

In terms of geographic details, the map includes a compass rose showing North, South, East, and West. A scale bar at the bottom measures distances up to 200 miles. Major geographic features such as the coastline and some islands off the southern coast are outlined.

The map shows that the northwestern coastal region of California experiences the highest precipitation levels. Central and southern inland areas, particularly the southeastern part, have much lower precipitation levels, indicated by red. The Sierra Nevada mountain range displays a gradient from high to moderate precipitation levels, transitioning from dark blue to green as it moves eastward. This map visually communicates the variation in precipitation across different regions of California during the first half of the 20th century.

Video 18.2.1: What is a Drainage Basin?

For our Geography Minute, what is a drainage basin? A drainage basin is an area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or another body of water. The drainage basin includes all surface water from rain runoff, snow melt, and any nearby streams that run downhill towards this shared outlet. This also includes the groundwater beneath the earth's surface.

The drainage basin acts like a funnel by collecting all this water within the area covered by the basin and channeling it into a single point once again, such as a river, bay, or another body of water. Other terms used interchangeably with drainage basin are catchment area, catchment basin, drainage area, river basin, and water basin. In North America, the term watershed is commonly used to mean a drainage basin.

I hope this has helped, because that's your Geography Minute!

Figure 18.2.2: Basic anatomy of drainage basins

This image is a three-dimensional diagram illustrating the concept of drainage basins and drainage divides. It depicts a landscape with two distinct drainage basins, each collecting water from its respective area.

The left side of the diagram represents the "Drainage basin of stream 1." This area is a network of tributaries, which are smaller streams that feed into a main stream. These tributaries collect precipitation runoff from the surrounding land and funnel it into the main stream, which flows towards a common outlet.

Similarly, the right side of the diagram shows the "Drainage basin of stream 2." Like the first basin, this area consists of tributaries that channel water into a main stream. The tributaries are interconnected, forming a branching pattern that effectively drains the surrounding landscape.

The "Drainage divide" is a ridge or elevated area that separates the two drainage basins. This divide determines the direction of water flow, ensuring that precipitation on one side flows into stream 1 and precipitation on the other side flows into stream 2. The divide prevents water from crossing over into the adjacent drainage basin.

This diagram illustrates how drainage basins and divides function in a landscape, highlighting the role of tributaries in collecting and channeling water and the importance of divides in directing the flow of water into separate basins.

Figure 18.2.3: Sacramento River

The image shows an aerial view of the Sacramento River displaying classic meandering river patterns. The river winds sinuously through the landscape, forming a series of pronounced loops and bends known as meanders. The surrounding terrain is a mix of agricultural fields and patches of woodland.

The meanders are well-defined, with some sections of the river nearly doubling back on themselves. This natural process occurs as the river erodes its outer banks and deposits sediment on the inner banks, gradually shifting its course over time. The varied colors and textures of the land, from the dark green of the forested areas to the lighter tones of the fields, highlight the contrast between the cultivated land and the natural river meanders.

The image provides a clear example of fluvial geomorphology, showcasing how rivers dynamically shape the landscape through erosion and deposition, creating the distinctive looping patterns characteristic of meandering rivers.

Figure 18.2.4: Satan Clara River, CA from the Air

The image shows an aerial view of the Santa Clara River in California, illustrating its characteristic braided stream formation. The river flows through a valley with multiple interconnected channels separated by wide sediment bars, which appear light-colored in contrast to the surrounding landscape. On both sides of the river, there are patches of agricultural fields and scattered urban development, indicating the river's proximity to human activity. The riverbed itself is wide, with several dry, sandy channels branching and rejoining, reflecting the river's dynamic and shifting nature. The surrounding terrain is a mix of rolling hills and mountainous areas, providing a backdrop to the river's braided pathways. The image captures the river's role in the local geography, demonstrating the interplay between natural river processes and land use in the region.

Figure 18.2.5: California Hydrologic Regions

This image is a detailed map of California, showing the state's various hydrologic regions along with county boundaries. The map is color-coded to differentiate between the hydrologic regions, each of which represents a distinct area based on water resources and watershed management.

The map highlights several hydrologic regions, each represented by a different color. The Central Coast region is marked in red, the Colorado River region in orange, the North Coast region in light blue, and the North Lahontan region in yellow. The Sacramento River region is depicted in dark blue, the San Francisco Bay region in purple, and the San Joaquin River region in green. The South Coast region is shown in light orange, the South Lahontan region in light green, and the Tulare Lake region in beige. These colors help to visually distinguish the different hydrologic areas within the state.

County boundaries are outlined with thin black lines, helping to distinguish the political boundaries within the state. The map labels major cities and counties, providing geographic context. Notable counties include Los Angeles, San Diego, Fresno, Sacramento, and San Francisco, among others, allowing viewers to easily identify key areas within each hydrologic region.

Additionally, the map marks the South Coast Regional Water Board boundaries with a red dashed line. This indicates the jurisdiction of the South Coast Regional Water Board, which oversees water quality in the South Coast region. This specific boundary helps to delineate areas of regulatory oversight, which is important for managing water quality and resources effectively.

Geographical features such as coastal areas, mountain ranges, and desert regions are also depicted on the map. These features are integral to understanding the state's water resources and hydrologic regions, as they influence the distribution and availability of water across California.

This map serves as a comprehensive representation of California's hydrologic regions. It illustrates how water resources are managed across different parts of the state and highlights the diversity of water resource management areas. The importance of regional planning in addressing water-related issues is emphasized, as different regions have unique challenges and resources that require tailored management strategies.

Figure 18.2.6: The Sacramento River Basin

This image is a map of the Sacramento River Basin, highlighting the extensive network of rivers and tributaries within the basin. The basin spans multiple counties in Northern California, each outlined and labeled for clear identification.

At the top of the map, the Sacramento River originates in Siskiyou County, flowing southward through Shasta, Tehama, Butte, Glenn, Colusa, Sutter, Yolo, and Sacramento counties. The map shows several major tributaries feeding into the Sacramento River, including the Pit River in Modoc and Lassen counties, the Feather River running through Plumas, Sierra, and Yuba counties, and the American River originating in El Dorado and Placer counties.

Other significant waterways are also depicted, such as Stony Creek in Glenn and Tehama counties, Cache Creek in Lake and Yolo counties, and Putah Creek which flows through Napa and Solano counties. The rivers and creeks are marked with blue lines, providing a clear visual representation of the hydrology within the basin.

The map includes a scale bar indicating distances of up to 50 miles, helping to understand the geographical scope of the Sacramento River Basin. A compass rose is located at the bottom right corner, indicating north to assist with orientation.

This map provides a detailed view of the Sacramento River Basin, showcasing the interconnected waterways that contribute to the river system. It highlights the importance of the basin in Northern California's water management and emphasizes the extensive network of rivers and tributaries that support the region's ecology and hydrology.

Figure 18.2.7: The San Joaquin River Basin

This image is a map of the San Joaquin River Basin, which highlights the intricate network of rivers and tributaries within the basin. The map spans multiple counties in central California, each outlined and labeled for easy identification.

The San Joaquin River Basin is depicted with the main San Joaquin River running prominently through the central part of the basin. The river flows from its headwaters in the Sierra Nevada through various counties including Fresno, Madera, Merced, Stanislaus, and San Joaquin before continuing to its confluence with the Sacramento River.

Several major tributaries feed into the San Joaquin River. To the north, the Calaveras River and the Mokelumne River flow through Calaveras and San Joaquin counties, while the Cosumnes River enters the basin from Sacramento County. To the east, the Tuolumne River runs through Tuolumne and Stanislaus counties, and the Merced River flows through Mariposa and Merced counties. Further south, the Chowchilla River and Fresno River contribute to the basin's network, flowing through Madera and Fresno counties.

The map also features numerous smaller tributaries and streams, providing a detailed view of the hydrological complexity within the basin. These waterways are marked with blue lines, illustrating the extensive water system that supports the region's ecology and water management needs.

The counties within the basin are clearly labeled, including Contra Costa, Alameda, Sacramento, San Joaquin, Calaveras, Amador, Tuolumne, Mariposa, Merced, Madera, and Fresno. This labeling helps to understand the geographical context and the political boundaries within the basin.

A scale bar at the bottom right corner of the map indicates distances of up to 50 miles, providing a reference for the size of the basin. Additionally, a compass rose in the bottom left corner indicates north, aiding in map orientation.

This map provides a comprehensive overview of the San Joaquin River Basin, highlighting its significant rivers and tributaries and the counties it spans. It emphasizes the importance of the basin in central California's water management and ecological health.

Figure 18.2.8: The San Joaquin Valley hydrology conceptual model by the United States Geological Survey

This image is a cross-sectional diagram depicting the hydrology of the San Joaquin Valley. The diagram illustrates various hydrological processes and land uses within the valley, emphasizing the interactions between surface water, groundwater, and land subsidence.

The landscape is divided into several zones. On the left side of the diagram, there are agricultural fields and orchards, indicating the extensive farming activities in the valley. Irrigation canals and rivers are shown supplying water to these fields. The agricultural activities are crucial for the region's economy but also significantly impact the valley's water resources.

The central part of the diagram highlights the "Area of land subsidence." This area shows the ground surface sinking due to the excessive extraction of groundwater. Wells are depicted extracting water from the underground aquifers, causing the land above to compress and subside. Arrows pointing downwards illustrate the movement of water from the surface into the subsurface, indicating recharge zones where water infiltrates the ground to replenish the aquifers.

The subsurface layers show the groundwater system, with water stored in porous rock and soil layers. Arrows within these layers indicate the flow of groundwater, moving towards areas of extraction and natural discharge points like springs and rivers. The diagram also shows the interaction between surface water and groundwater, with arrows depicting the movement of water between these two systems.

On the right side of the diagram, there is a mountainous region, representing the Sierra Nevada, which is a significant source of water for the valley through snowmelt and runoff. Streams and rivers originating from the mountains contribute to the valley's surface water supply.

This diagram provides a clear and informative visualization of the hydrological processes in the San Joaquin Valley. It highlights the critical issues of groundwater extraction and land subsidence, showing how agricultural activities and water management practices impact the region's hydrology. The diagram emphasizes the need for sustainable water use and management to address the challenges of land subsidence and water scarcity in the valley.

Figure 18.2.9: The Tulare Lake River Basin by the California Department of Conservation

This image is a map of the Tulare Lake River Basin, showcasing the intricate network of rivers and their tributaries within the basin. The map outlines the basin, which spans several counties in central California.

The Tulare Lake River Basin includes prominent rivers such as the Kings River, the Kaweah River, the Tule River, and the Kern River. These rivers are marked in blue, highlighting their course through the basin. The Kings River flows from the Sierra Nevada mountains through Fresno County, while the Kaweah River and Tule River flow through Tulare County. The Kern River flows south through Kern County, contributing significantly to the water supply in the region.

The map indicates the county boundaries within the basin, with major counties including Fresno, Kings, Tulare, and Kern. These boundaries help to identify the areas affected by the basin's hydrology.

Additionally, the map provides geographical context by including neighboring counties and cities. Counties such as San Benito, San Luis Obispo, Ventura, and Los Angeles are marked, though they are outside the basin boundaries. This helps to understand the broader regional setting of the Tulare Lake River Basin.

A scale bar at the bottom left corner of the map indicates distances of up to 50 miles, offering a reference for the size and extent of the basin. A compass rose located nearby indicates the direction of north, aiding in map orientation.

This map provides a clear and detailed view of the Tulare Lake River Basin, emphasizing the major rivers and their flow through the region. It highlights the importance of these watercourses for the counties within the basin and underscores the need for effective water management to support the area's agricultural and ecological needs.

Figure 18.3.1: Types of aquifers by Ralph C. Heath

This image is a cross-sectional diagram illustrating different types of groundwater wells and the geological layers they penetrate. The diagram is divided into two main zones: the unsaturated zone and the saturated zone.

The uppermost layer is labeled "Land," which covers the ground surface. Beneath this is the unsaturated zone, where the soil and rock contain air and water in their pores but are not fully saturated with water.

Below the unsaturated zone is the saturated zone, which contains two main types of aquifers: the unconfined aquifer and the confined aquifer.

The unconfined aquifer is the uppermost water-bearing layer, consisting of sand. This aquifer is directly influenced by surface conditions and is separated from the atmosphere only by the unsaturated zone. The water table marks the upper surface of the unconfined aquifer, indicating the level at which the ground is fully saturated with water.

Within the unconfined aquifer, there is a "Water-table well," which extends from the land surface down to the water table. This well is designed to draw water directly from the unconfined aquifer. The well screen at the bottom of the well allows water to enter while filtering out sediments.

Beneath the unconfined aquifer is a "Confining Bed" composed of clay, which acts as an impermeable layer preventing water from moving freely between the unconfined aquifer and the underlying confined aquifer.

The confined aquifer lies below the confining bed and is typically made up of permeable materials such as limestone. This aquifer is under pressure because it is trapped between two impermeable layers.

The diagram also shows an "Artesian well" that penetrates through the confining bed into the confined aquifer. Artesian wells tap into pressurized groundwater, which can rise up the well without the need for pumping, often reaching the surface naturally. The "Potentiometric surface" in the diagram indicates the level to which water will rise in tightly cased wells.

This diagram provides a detailed understanding of groundwater systems, illustrating the different types of wells, their construction, and the geological layers they interact with. It highlights the dynamics of groundwater movement and the importance of aquifer and confining layers in groundwater management.

Figure 18.3.2: Aquifer conditions and water flow by Hans Hillwaert

This image is a cross-sectional diagram depicting groundwater flow and aquifer systems, focusing on the interactions between unconfined and confined aquifers, the unsaturated zone, and surface features such as streams and vegetation.

The diagram is divided into several layers, each representing different components of the groundwater system. At the top, the land surface is shown with trees and a stream, indicating the presence of surface water and vegetation.

Below the land surface is the unsaturated zone, where the soil and rock contain both air and water in their pores but are not fully saturated. The water table marks the boundary between the unsaturated zone and the saturated zone below it. The water table can be seen intersecting with the stream, illustrating how surface water and groundwater are connected.

The saturated zone contains two main types of aquifers: the unconfined aquifer and the confined aquifer. The unconfined aquifer is the uppermost water-bearing layer, depicted with a high hydraulic-conductivity aquifer material (colored light blue). This aquifer is directly influenced by surface conditions and extends down to the confining layer below it.

The confining layer, marked by low hydraulic-conductivity material (colored with a dashed pattern), separates the unconfined aquifer from the confined aquifer beneath it. The confined aquifer lies below this confining layer and is depicted with high hydraulic-conductivity material, similar to the unconfined aquifer. This confined aquifer is under pressure due to the overlying confining layer and surrounding geological formations.

Groundwater flow is indicated by arrows within the aquifers, showing the movement of water from areas of recharge (where water enters the aquifer) to areas of discharge (where water exits the aquifer, such as into the stream or through wells). The direction of groundwater flow is influenced by the hydraulic gradient and the permeability of the geological materials.

The diagram also shows the processes of transpiration by vegetation, where water is taken up by plant roots and released into the atmosphere through leaves. This process affects the groundwater levels and the overall hydrology of the area.

The legend at the bottom of the diagram explains the color coding: light blue represents high hydraulic-conductivity aquifers, dashed blue represents low hydraulic-conductivity confining units, and a solid tan color represents very low hydraulic-conductivity bedrock. The arrows indicate the direction of groundwater flow.

This diagram provides a comprehensive view of the groundwater system, illustrating the interactions between different aquifer types, surface water, and the processes that influence groundwater movement. It emphasizes the importance of understanding these interactions for effective water management and conservation.

Figure 18.3.3: Artesian aquifer conditions and well flow by Andrew Dunn

This image is a cross-sectional diagram illustrating the concept of an artesian well within a groundwater system. The diagram shows the different geological strata, including pervious (permeable) and impervious (impermeable) layers, and how they interact to create conditions for an artesian well.

The pervious strata, colored in light blue, are layers of rock or sediment that allow water to pass through them easily. These layers are typically made of materials such as sand, gravel, or fractured rock. The impervious strata, colored in grey, are layers that do not allow water to pass through easily. These are usually composed of dense materials like clay or unfractured rock.

The diagram shows a curved structure of geological layers, with the pervious strata forming an aquifer confined between impervious strata. This configuration creates a confined aquifer system, where water is trapped under pressure between the impermeable layers.

The saturation level is indicated by a dashed line, showing the highest level to which water can rise in the aquifer under natural pressure conditions. When a well is drilled into the confined aquifer, the pressure forces the water to rise above the level of the aquifer, often reaching the surface without the need for pumping. This type of well is called an artesian well, illustrated in the diagram by the upward flow of water from the well.

The artesian well is shown tapping into the confined aquifer, with water flowing upwards due to the pressure created by the surrounding impervious layers. This pressure can cause the water to rise significantly above the aquifer, sometimes even resulting in a free-flowing well.

The diagram highlights the importance of geological formations in creating artesian conditions, where natural pressure can be utilized to access groundwater. It also emphasizes the role of pervious and impervious strata in determining the movement and availability of groundwater in an aquifer system.

Figure 18.3.4: California Aquifers by geographic location. “California’s Aquifers” by Cole Heap

This map illustrates the various aquifer systems across the state of California, highlighting the geographic distribution and types of aquifers with color-coding for easy identification. The map includes California's major cities, such as San Francisco, Sacramento, Fresno, Los Angeles, and San Diego, as well as important geographic features, including the coastline and major mountain ranges.

The six different types of aquifers highlighted and color-coded on the map include Basin and Range basin-fill aquifers, Basin and Range carbonate-rock aquifers, California Coastal Basin aquifers, Central Valley aquifer system, Pacific Northwest basaltic-rock aquifers, and Pacific Northwest basin-fill aquifers. Basin and Range basin-fill aquifers, shown in light green, are found primarily in the eastern part of the state and extend into parts of the central and southern regions. Basin and Range carbonate-rock aquifers, depicted in purple, are scattered in smaller patches, particularly in the eastern areas. California Coastal Basin aquifers, marked in teal, are concentrated along the coastal regions, extending from the north near San Francisco down to the south near San Diego. The Central Valley aquifer system, shown in gray, dominates the central part of California, encompassing the extensive agricultural regions of the Central Valley. Pacific Northwest basaltic-rock aquifers, indicated in red, are located in the northern part of the state. Pacific Northwest basin-fill aquifers, marked in blue, are also found in the northern regions, overlapping slightly with the basaltic-rock aquifers.

The map includes a compass rose indicating the cardinal directions and a scale bar for reference, showing distances in miles. Additionally, a legend is provided to clarify the color-coding of the different aquifer types, making it easier to understand the distribution and types of groundwater systems present throughout California.

Figure 18.4.1: Water storage and distribution in California. ​​Blue: California State Water Project (SWP) infrastructure

The map titled "Water Storage & Distribution in California" illustrates the complex network of reservoirs, canals, aqueducts, and rivers that manage and distribute water throughout the state. The infrastructure is categorized and color-coded for clarity. The Central Valley Project (CVP) infrastructure is marked in red, SWP–CVP shared infrastructure in purple, other federally owned/operated infrastructure in green, and state and private infrastructure in gray. Rivers are denoted with light blue lines, providing a natural context for the man-made water systems.

The map uses bold letters and colored squares to denote reservoirs, with the size of the squares indicating their capacity. Large squares indicate reservoirs of over 2 million acre feet (1.6 km³) capacity, medium squares indicate reservoirs of 1–2 million acre feet (0.8–1.6 km³), small squares indicate reservoirs of 250,000–1 million acre feet (0.3–0.8 km³), and smaller squares indicate reservoirs of less than 250,000 acre feet (0.3 km³). Additionally, bold italic letters and colored (except light blue) lines denote canals and aqueducts.

Some key reservoirs on the map include Trinity and Shasta in the north, Oroville and Folsom in the central region, and San Luis and New Melones in the south. Major canals and aqueducts, such as the California Aqueduct and the Colorado River Aqueduct, are prominently marked, highlighting the extensive infrastructure required to transport water across California's diverse landscape. This map provides a comprehensive view of California's water storage and distribution system, emphasizing the importance of managing water resources in a state with varied climate and geographic conditions.

The image depicts an illustration of a large dam, the Auburn Dam, showcasing its structure and the reservoir it creates. The dam appears to be an arch dam, a type of dam curved upstream and designed to transfer the weight of the water it holds back into the surrounding rock walls. The illustration highlights the massive scale of the dam, with the reservoir extending into the background, indicating a substantial water storage capacity. This kind of infrastructure is essential for water management, providing water for irrigation, flood control, hydroelectric power generation, and recreational purposes. The surrounding landscape, depicted with lush greenery and hilly terrain, suggests that the dam is situated in a region with significant topographical variation, which is typical for such large-scale dam projects. The engineering and construction of such dams are crucial for sustainable water resource management, particularly in regions with variable water availability.

Video 18.4.1: State Water Project: An Aerial Tour

The California State Water Project starts its journey in the peaks of the Sierra Nevada Mountains in Northern California, where most of California's rain and snow fall each year. The three Upper Feather River lakes, Antelope, Frenchman, and Davis, sit at the top of the State Water Project. Antelope Lake, which is the smallest of the Upper Feather River lakes, is located on Indian Creek, a tributary of the east branch of the North Fork Feather River.

To the southeast is Frenchman Lake, the first lake created for the SWP in 1961, which consists of 21 miles of shoreline and a 139-foot-tall earthen dam. Lake Davis is located on Big Grizzly Creek, a tributary of the Middle Fork Feather River. It is the largest of the three lakes with a capacity of more than 84,000 acre-feet.

The Upper Feather River lakes feed into the North and Middle Forks of the Feather River, which wind their way through Plumas County, providing local water supply along the way. Along the Middle Fork of the Feather River, the freshwater cascades over Feather Falls, a picturesque recreation destination. The Forks of the Feather River feed into Lake Oroville, which is contained by Oroville Dam, the tallest dam in the United States at 770 feet.

Constructed in the 1960s, Lake Oroville is the second-largest reservoir in California and can store more than 3.5 million acre-feet of water. In addition to Oroville Dam, the Oroville Thermolito Complex includes three power plants, Hyatt, Thermolito Diversion Dam, and Thermolito Pumping Generating Power Plant, which together can produce 835 megawatts of electricity, enough clean hydropower to power 1.6 million homes for a year. While its primary purposes are water supply, hydroelectricity generation, and flood control, Lake Oroville also offers a variety of recreation opportunities.

Water continues from Lake Oroville down the Feather River until it meets up with the Sacramento River in southern Sutter County, just north of Sacramento. From there, the water heads south along the Sacramento River, winding its way through the farmlands of the northern Sacramento Valley, through downtown Sacramento, and into California's Sacramento-San Joaquin Delta. Once in the Delta, water is diverted to different parts of the state.

The Cordelia Pumping Plant in Solano County is part of the North Bay Aqueduct System, which provides water to cities in Napa and Solano counties. Water is pumped from the Delta at Barker Slough Pumping Plant and travels over 27 miles in an underground pipeline to its storage terminus in the city of Napa. Further south, water from the Delta is moved to the Clifton Court Forebay in Contra Costa County.

This shallow reservoir sits at the southern end of the Delta and provides storage and flow regulation into the Banks Pumping Plant. At Banks Pumping Plant, water is pumped up a hillside 244 feet to start its journey south, along the 444-mile-long California Aqueduct. The plant includes 11 pumps to move water into the canal and divert water during wet months to off-stream storage reservoirs and groundwater basins south of the Delta to improve water supply reliability.

Just a mile downstream from the Banks Pumping Plant, Bethany Reservoir marks the beginning of the South Bay Aqueduct. Here, the South Bay Pumping Plant moves water to the west to serve communities in Alameda and Santa Clara counties. Along the way, Lake DelVal in Alameda County provides storage and flood control for the South Bay Aqueduct.

Back in the Central Valley, the California Aqueduct stretches south through hundreds of miles of farmland and towns. The aqueduct is the most recognized facility in the State Water Project. It is the primary method for transporting water from northern California to southern California.

The concrete-lined canal winds its way through the valley and travelers along Interstate 5 can see the glistening waters of the canal. The California Aqueduct moves water by gravity with a little help from pumping plants along the way. Along the western side of the Central Valley in Merced County, the California Aqueduct enters O'Neill Forebay.

This body of water is part of the larger San Luis Reservoir Joint Use Complex that serves both the State Water Project and the Federal Central Valley Project. San Luis Reservoir is the nation's largest off-stream reservoir. The reservoir stores water diverted from the Sacramento-San Joaquin Delta for later deliveries to the South Bay Area, Central Valley, Central Coast, and Southern California.

Overlooking San Luis Reservoir is the Romero Visitor Center. Romero offers exhibits and videos that highlight California's world-renowned water delivery system and the importance of water in our lives, along with impressive views of the reservoir. With no watershed to support San Luis, the Gianelli Pumping Generating Plant moves water from the O'Neill Bay into San Luis Reservoir.

The plant generates electricity when water flows are reversed. To the south of San Luis, the Dos Amigos Pumping Plant gives water a 113-foot lift as it continues along the California Aqueduct. Further south is another important branch of the California Aqueduct.

The Coastal Branch Aqueduct provides water for San Luis Obispo and Santa Barbara counties. Water travels through the Coastal Branch Aqueduct to several pumping plants and ends near Vandenberg Air Force Base. Back on the main aqueduct, Buena Vista Pumping Plant, located south of Bakersfield in Kern County, sends the water on the next leg of its journey.

The plant is the first in a series of lifts known as the Valley String Pumping Plants. Here, water is sent up 205 feet. Just a few miles down the aqueduct is T-Rink Pumping Plant.

This facility provides the second lift, moving water up another 233 feet. Just a little further downstream, Chrisman Pumping Plant provides another lift. Here, State Water Project Water is lifted 518 feet for its journey over the Tehachapi Mountains, courtesy of the Edmonston Pumping Plant.

Now it's time for the big lift. Considered one of California's engineering marvels, Edmonston Pumping Plant uses 14 80,000 horsepower pumps to lift water 1,926 feet over the Tehachapi Mountains. The plant is the highest single-lift pumping plant in the world.

From there, water flows through a series of tunnels into the Tehachapi Afterbay, where the aqueduct divides into the West Branch and East Branch of the California Aqueduct. The West Branch of the State Water Project moves water to millions of Californians in Los Angeles and other cities in Southern California. Oso Pumping Plant is the first major structure on the West Branch of the California Aqueduct.

It lifts water 231 feet from Tehachapi Afterbay to Quail Canal, which leads into Quail Lake. From Quail Lake, State Water Project Water travels to Pyramid Lake in Los Angeles County. Visible from Interstate 5, Pyramid Lake provides storage for deliveries from the West Branch and recreational opportunities.

The lake is contained by the 400-foot-tall Pyramid Dam at the southern end of the lake. Pyramid Lake is also home to the Vista del Lago Visitor Center, which offers exhibits on the State Water Project and stunning views of the lake. Further south, Castaic Lake serves as the terminus of the West Branch.

The lake provides storage for the State Water Project as well as recreation opportunities in the Southern California area. The lake is contained by the 425-foot-tall Castaic Dam. Back at the junction, the East Branch of the State Water Project moves water through the Antelope Valley to communities like Riverside and San Bernardino.

The water is used by residents as well as groundwater recharge. Pear Blossom Pumping Plant is located along the East Branch of the California Aqueduct, about 12 miles east of the town of Palmdale. The plant lifts water about 540 feet to continue its journey southeast by gravity to Silverwood Lake.

The newest State Water Project power plant, the Mojave Siphon Power Plant, completed in 1996, generates electricity from the water flowing back downhill on its way to Silverwood Lake. Cedar Springs Dam, a 249-foot-tall earthen dam, creates Silverwood Lake. Located about 30 miles north of the city of San Bernardino, the lake provides regulatory and emergency storage, ensuring deliveries to users along the East Branch, and provides recreation for local communities.

Silverwood Lake also serves to ensure continuity of discharges through the Devil Canyon Power Plant. Devil Canyon Power Plant is situated at the southern base of the San Bernardino Mountains, about 5 miles north of San Bernardino. The power plant generates electricity from water traveling through the plant from Silverwood Lake.

From Devil Canyon, water is moved along the East Branch extension to Crafton Hills Reservoir. This reservoir provides additional storage and water supply for the east side of San Bernardino County. Back on the main segment of the East Branch Aqueduct, Lake Paris in Riverside County marks the end of the lawn.

It is the southernmost State Water Project reservoir and provides water supply and recreation. It's one of the most popular recreational lakes in the State Water Project system. From the headwaters of the Feather River Watershed to the reservoirs of Southern California, DWR's State Water Project provides critical water supply to millions of Californians, thanks to world-class engineering and some help from Mother Nature.

DWR is committed to ensuring the system continues to operate safely and efficiently for generations to come.

Figure 18.4.3: View across Hetch Hetchy Valley, early 1900s, from the southwestern end, showing the Tuolumne River flowing through the lower portion of the valley prior to damming.

The black and white photograph showcases a vast valley flanked by towering cliffs, with two prominent waterfalls cascading down the rock faces. The valley floor is a mosaic of meandering streams, lush vegetation, and open meadows, suggesting a fertile and dynamic landscape shaped by natural water flows. The surrounding cliffs exhibit rugged, exposed rock formations, hinting at the geological history and forces that have sculpted this terrain over millennia. The overall scene conveys a sense of untouched natural beauty, highlighting the interplay between water, rock, and vegetation in this dramatic landscape. This image is a testament to the awe-inspiring power of nature and the intricate processes that continue to shape our planet's surface.

Figure 18.4.4: Hetch Hetchy Panorama – Yosemite National Park in 2019 by Vulpinus2

The color photograph displays a serene lake framed by majestic cliffs, under a clear blue sky with a few scattered clouds. The water is calm, reflecting the surrounding landscape. The cliffs rise dramatically from the lake, showcasing their rugged, rocky textures. In the distance, the remnants of waterfalls can be seen, hinting at the geological processes that have shaped this region. The lush greenery along the cliffs contrasts with the barren rock, indicating the presence of vegetation adapted to this environment. This modern-day image, compared to the previous black and white photo, illustrates the enduring natural beauty of this landscape, capturing its timeless essence while highlighting the subtle changes that have occurred over time.

Figure 18.4.5: Aerial photo of the California Aqueduct

The image shows an aerial view of the California Aqueduct, a large man-made waterway winding through a vast, dry landscape. The aqueduct appears as a dark blue or black channel that snakes through the arid terrain, which is predominantly light brown and sparsely vegetated, indicating a desert or semi-arid region.

The aqueduct is lined with concrete and follows a curving path, with several sharp bends and turns. There are multiple parallel channels and branches visible, suggesting a complex network of waterways designed to distribute water across the region. The surrounding land includes a mix of agricultural fields, patches of barren land, and scattered buildings or structures, likely farms or small settlements.

In the background, there is a larger, more densely built-up area, possibly a town or industrial complex, indicating human habitation and activity in the region. The sky is clear, with no visible clouds, suggesting a sunny day. The image highlights the contrast between the engineered waterway and the natural, arid landscape it traverses, showcasing the critical role of the aqueduct in providing water to this dry region of California.

Figure 18.4.6: Levee Around a Sacramento Suburb

The image shows an aerial view of a suburban area in Sacramento, California, surrounded by a levee. The suburb is characterized by numerous houses and tree-lined streets. The houses are primarily single-family homes, and the area appears to be densely populated with a mix of evergreen and deciduous trees providing significant greenery.

A river runs alongside the suburb, bordered by the levee, which is a raised embankment designed to prevent flooding. The levee is covered with grass and follows the curve of the river, creating a natural barrier between the water and the residential area. Beyond the suburb and river, the landscape transitions into flat, expansive farmland with large, open fields stretching towards the horizon. The sky is mostly clear, suggesting a calm and pleasant day. The image captures the integration of urban development, natural vegetation, and agricultural land in this region of Sacramento.

Figure 18.5.1: Saltwater-freshwater interface along the coast by Jooja

The cross-section diagram illustrates the interaction between fresh water and saltwater in a coastal aquifer system. The land surface, composed of sand, lies above the water table, which is the upper surface of the zone where the soil or rocks are permanently saturated with water. Freshwater, indicated in light blue, floats above the denser saltwater, represented in blue with diagonal lines, which intrudes from the sea. The interface between the fresh water and saltwater slopes downward beneath the land surface, maintaining a dynamic equilibrium. The thickness of the freshwater lens is denoted by 'h', while 'z' indicates the depth to the interface below sea level. The sea level serves as the reference point for both the water table and the position of the interface. The diagram highlights the importance of managing groundwater resources to prevent saltwater intrusion, which can compromise the quality of freshwater supplies. This understanding is crucial for sustainable water management in coastal regions.

Figure 18.5.2: USGS studies show that the geology of the Los Angeles Basin is highly complex

The diagram presents a modeled condition of a coastal aquifer system from the year 2004, showcasing the distribution of chloride concentrations along a cross-sectional view from point A to A'. The vertical axis represents depth in meters below the North American Vertical Datum of 1988 (NAVD 88), while the horizontal axis indicates distance along the section in meters. The cross-section includes various geological layers, with depths ranging from the surface to over 800 meters below.

The coastline is marked at around the 10,000-meter mark on the horizontal axis, and several wells are indicated along the section. The explanation box in the diagram provides a color-coded key for simulated chloride concentrations in milligrams per liter, ranging from 2,000 mg/L (blue) to 18,000 mg/L (red). Higher chloride concentrations, depicted in red and orange, are found closer to the coastline, signifying areas of significant saltwater intrusion.

Geological formations such as Pliocene B and C, and Tertiary undifferentiated units are labeled in the cross-section, showing the variation in sediment layers and their influence on groundwater flow and chloride distribution. Wells, such as 5S/13W-11P 1.2 and 5S/13W-2E 1.2, are positioned at different points along the section to monitor and analyze the chloride concentrations and groundwater conditions.

This detailed illustration underscores the complexity of coastal aquifer systems and the importance of monitoring chloride levels to manage and mitigate saltwater intrusion, which can impact freshwater resources. The vertical exaggeration of 5:1 enhances the visualization of the geological formations and the distribution of chloride concentrations.

Figure 18.5.3: Salt water intrusion by Brown and Caldwell, released to California Department of Water Resources

This map illustrates the progression of seawater intrusion into an aquifer system over several decades, specifically focusing on the area around Marina, California. The different colors on the map represent the extent of seawater intrusion in various years, with each color corresponding to a different period.

In 1944, seawater intrusion was limited to a small area along the coast. By 1965, the intrusion had spread inland, encompassing a larger area. This trend continued over the years, with significant expansion noted in 1975, 1985, and 1993. By 1997 and 1999, seawater had intruded further into the aquifer system, indicating a persistent and growing problem.

The map also marks the extent of seawater intrusion for specific years, including 2001, 2003, 2005, 2007, 2009, and 2011, highlighting the continued advance of seawater into the aquifer. The blue line indicates the 2013 seawater intrusion extent, defined by a 500 mg/L chloride concentration contour.

Key infrastructure and landmarks such as Nashua Road, Blanco Road, and Reservation Road are shown on the map, providing geographical context. The map underscores the significant and ongoing challenge of managing seawater intrusion in coastal aquifers, necessitating effective groundwater management strategies to protect freshwater resources.

Figure 18.5.4: Salinas Valley Basin groundwater elevation by Monterey County Water Resources Agency

This map depicts the groundwater elevation in the Salinas Valley Basin as of August 2019, focusing on the Pressure 180-Foot and East Side Shallow Aquifers. The red contour lines represent lines of equal groundwater elevation, with each line indicating a 10-foot change in elevation.

The groundwater elevations range from -100 feet to +40 feet, showing significant variation across the basin. The map highlights a potential fault zone with a dotted line running through the central part of the basin, potentially influencing groundwater movement and distribution.

Key locations are marked, including Castroville to the north, Salinas at the center, Marina to the west, and Chualar to the south. The Monterey Bay is shown to the west, providing context for the basin's proximity to the coast.

The contour lines illustrate the groundwater flow direction, which generally moves from higher elevations in the east towards lower elevations near the coast and the Monterey Bay. This flow pattern is crucial for understanding groundwater management and addressing issues such as seawater intrusion, which can affect the quality and availability of groundwater in the basin.

The map provides a detailed snapshot of groundwater conditions in the Salinas Valley Basin, serving as a valuable tool for water resource management and planning in the region.

This diagram illustrates the interaction between production wells and barrier wells in managing the saltwater interface.

On the left side, a production well is depicted, which extracts groundwater from the subsurface. The arrows pointing towards the well indicate the direction of groundwater flow towards the well as it is pumped out. The production well taps into the groundwater reservoir, drawing freshwater up to the surface for use.

On the right side, a barrier well is shown, designed to prevent saltwater intrusion into freshwater aquifers. The arrows around the barrier well illustrate the direction of water movement, with water being injected into the aquifer to create a pressure barrier. This barrier well pushes the saltwater interface back towards the sea, maintaining the separation between freshwater and saltwater.

The saltwater interface is the boundary where freshwater meets saltwater. In coastal areas, over-pumping of groundwater can lead to saltwater moving inland, contaminating freshwater supplies. The diagram shows the sea level and the position of the saltwater interface under natural conditions.

Overall, this setup helps manage the balance between freshwater and saltwater, ensuring sustainable groundwater extraction while preventing saltwater intrusion.

Figure 18.5.6: Conceptual diagram of saltwater pumping by a barrier well by the United States Geological Survey

The diagram consists of three parts (A, B, and C), which illustrate the process of saltwater intrusion and the use of injection wells to create a barrier against it.

In part A, we see a pumping well extracting freshwater from an aquifer. The potentiometric surface, which is the level to which water will rise in tightly cased wells, is shown above the aquifer. The aquifer is confined by a layer of impermeable material, preventing water from moving freely upwards. Under normal conditions, the freshwater in the aquifer keeps the saltwater at bay, maintaining a stable interface between the two.

In part B, continued pumping from the well creates a cone of depression in the potentiometric surface around the well. This lowers the water level in the aquifer, reducing the pressure that holds back the saltwater. As a result, a saltwater wedge begins to intrude into the freshwater zone. This intrusion can compromise the quality of the extracted water, as the well starts to draw in saltwater.

In part C, an injection well is used to address the issue of saltwater intrusion. Water is injected into the aquifer through this well, creating a pressure gradient that forms a barrier against the advancing saltwater wedge. This injected water raises the potentiometric surface and helps to push the saltwater back towards the sea, protecting the freshwater resources in the aquifer from contamination.

This process demonstrates how managing groundwater extraction and using injection wells can help maintain the balance between freshwater and saltwater, ensuring a sustainable supply of clean groundwater.

Figure 18.5.7: Basin Prioritization of 2019. “California Sustainable Groundwater Management Act (SGMA) Basin Prioritization” by Cole Heap

This map, titled "California Sustainable Groundwater Management Act (SGMA) Basin Prioritization," categorizes various groundwater basins in California based on their priority levels for sustainable management as mandated by SGMA. The map delineates four priority levels: high, medium, low, and very low. High-priority basins are marked with dense diagonal stripes, medium-priority basins with lighter diagonal stripes, low-priority basins with a pale shade, and very low-priority basins with a very light shade.

The high-priority basins, which are crucial for groundwater management due to their significant role in California's water supply and potential challenges, are concentrated in regions with intensive agricultural activities, high population densities, or both. These areas include parts of the Central Valley, particularly around Fresno and Sacramento, and extend to other regions like San Francisco and San Jose.

Medium-priority basins, which also play an important role but with slightly less urgency, are scattered throughout the state, including areas near Los Angeles and parts of the Central Coast.

Low-priority and very low-priority basins, which have less immediate management needs, cover large portions of the state, particularly in regions with less intensive water use or lower population densities. These areas include much of Northern California outside the Central Valley and extensive parts of Southern California.

The map also includes a small inset showing California's location within the United States, providing a broader geographical context. Additionally, it highlights significant urban centers like Los Angeles, San Diego, and San Francisco, emphasizing the relationship between population centers and groundwater basin prioritization.

The map was created by Cole Heap, P.G., and uses data from the USGS, SGMA 2019 Basin Prioritization report, and various other geographical and environmental sources. It provides a visual guide for understanding the areas where sustainable groundwater management efforts are most needed in California.

Figure 18.5.8: Dry lakebed in California

This image shows a scene of severe drought, characterized by a significantly low water level and cracked, dry ground. The remaining water in the background forms a small, narrow body, indicating that this area was once fully submerged. The trees lining the sides of the water body suggest a natural environment, possibly a lake or reservoir, now drastically reduced in size due to the lack of rainfall or overuse of water resources. The dry, parched soil in the foreground highlights the extent of the drought's impact, with deep fissures and cracks illustrating the severity of the arid conditions.

Figure 18.5.9: Satellite images-Lake Oroville by the United States Geological Survey

This image shows a side-by-side comparison of Lake Oroville on June 4, 2019, and June 9, 2021, highlighting the impact of drought conditions over two years. The 2019 image depicts Lake Oroville with high water levels, covering a vast area with dense greenery surrounding the lake. The water appears deep and expansive, indicating a period of ample rainfall or water supply.

In contrast, the 2021 image shows a significantly reduced lake size, with much of the lakebed exposed and the water levels drastically lower. The exposed lakebed is a lighter color, indicating dryness and the absence of water. The surrounding areas also appear less green, suggesting vegetation stress or die-off due to prolonged dry conditions. The reduction in water levels over the two-year period is stark, illustrating the severe impact of drought on Lake Oroville and its ecosystem. The visual difference between the two images serves as a powerful illustration of the changing environmental conditions and the challenges posed by water scarcity.

Figure 18.5.10: Progression of the 2012-2014 historic California drought by the National Drought Mitigation Center

This animated image shows the progression of drought conditions across California from December 31, 2013, to July 29, 2014, as reported by the National Drought Mitigation Center. The animation highlights different levels of drought severity, marked by color codes: yellow for abnormally dry, orange for moderate drought, light red for severe drought, dark red for extreme drought, and brown for exceptional drought.

At the beginning of the animation on December 31, 2013, the central and southern parts of California are already experiencing severe to extreme drought, while the northern regions are mostly abnormally dry or under moderate drought. As the animation progresses through the months, the drought conditions intensify and spread. By July 29, 2014, the entire state is engulfed in drought, with large areas under extreme or exceptional drought conditions, particularly in the Central Valley and parts of Southern California. This stark visual progression underscores the worsening water scarcity and the environmental stress facing the state over this period.

Figure 18.5.11: Flooding in California’s Sacramento Valley (MODIS)

This satellite image, taken from a broad perspective, showcases the northern California region with a specific emphasis on the Sutter Buttes, which is marked with an arrow. The Sutter Buttes are a small circular range of volcanic hills in the Central Valley of California, often referred to as the "smallest mountain range in the world."

In the image, different shades of green indicate various types of vegetation and land cover, while the blue and cyan tones suggest the presence of water bodies and snow. The dark areas represent bodies of water, including rivers, lakes, and reservoirs. The Sutter Buttes stand out as a distinct feature in the otherwise flat landscape of the Central Valley.

The surrounding landscape includes fertile agricultural fields, evident by the patchwork pattern, as well as natural vegetation in the hills and mountains. To the west, the Pacific Ocean is visible, and the coastal areas appear dark due to the dense forest cover. The urban areas, such as the San Francisco Bay, show a mix of colors indicating the complex land use in these regions. This image provides a detailed view of the diverse geography and land use in northern California, highlighting both natural and human-modified landscapes.

Figure 18.5.12: Permeable Pavement sign in Grass Valley, California

The informative sign titled "Permeable Pavement" explains the concept and process of using permeable pavement to manage stormwater. It provides a comprehensive overview of how permeable pavement works, its benefits, and the specific implementation in the surrounding area. The top section illustrates the structure of permeable pavement. It includes a surface layer of permeable material that allows water to pass through. Beneath this layer, there are additional layers designed to filter and store water, eventually allowing it to seep into the ground below. This process reduces runoff and helps recharge groundwater.

The main process involves rainwater that falls on the permeable pavement. Instead of running off into storm drains, the water infiltrates through the pavement and the underlying layers of gravel and sand. This filtered water then recharges the groundwater system. The sign also highlights the journey of water from the permeable pavement into nearby creeks and rivers, emphasizing the environmental benefits such as reduced erosion and improved water quality.

The bottom part of the sign details the local implementation of permeable pavement in the area. It describes how the permeable pavement on N. School Street contributes to the health of local water bodies, such as Grass Valley and Wolf Creek. The sign also provides visual aids, including a map and illustrations, to help viewers understand the connection between the permeable pavement and the local watershed. This sign serves as an educational tool for the public, promoting awareness of sustainable stormwater management practices and their positive impact on the environment. It encourages the use of permeable pavement as a practical solution for reducing urban runoff and enhancing groundwater recharge.