6.5: Irrigation

Just as there were major investments in mechanical technologies to increase the productivity of labor, there were also substantial investments to increase the productivity of California’s land. These included agro-chemical research, biological learning concerning appropriate crops and cultural practices, and land clearing and preparation; but the most notable were investments in water control and provision. These took two related forms. The first consisted of measures primarily intended to drain and protect agricultural land from flooding. In this realm, Californians literally re- shaped their landscape as individual farms leveled the fields and constructed thousands of miles of ditches. In addition, individual farms, reclamation districts, and the Army Corps of Engineers built several thousand miles of major levees to tame the state’s inland waterways. Without these investments, much of the Central Valley’s land could not have been planted in intensive crops.

The second form consisted of a variety of measures to supply the state’s farms with irrigation water. Expansion occurred in two main waves: the first lasting from 1900 through the 1920s and the second, linked to the Central Valley Project, during the decade after World War II. Much of the historical growth of irrigation was the result of small-scale private initiatives rather than large-scale public projects that have attracted so much scholarly attention. Up until the 1960s, individuals and partnerships were the leading forms of organization supplying irrigation water. These forms accounted for roughly one-third of irrigated acres between 1910 and 1930, and over one-half by 1950.

These small-scale irrigation efforts were closely associated with the rising use of groundwater in California over the first half of the twentieth century. Between 1902 and 1950, the acreage irrigated by groundwater sources increased more than thirty-fold, whereas that watered by surface sources only tripled. Groundwater, which had supplied less than 10 percent of irrigated acreage in 1902, accounted for over 50 percent of the acreage by 1950. This great expansion was reflected in the growing stock of pumping equipment in the state. Significant technological changes in pumping technology and declining power costs underscored this growth. During the 1910s and 1920s, the number of pumps, pumping plants, and pumped wells doubled each decade, rising from roughly 10,000 units in 1910 to just below 50,000 units in 1930. Pumping capacity increased two-and-one-half to three times per decade over this period. Expansion stalled during the Great Depression but resumed in the 1940s with the number of pumps, plants, and wells rising to roughly 75,000 units by 1950. Individuals and partnerships dominated pumping, accounting for about 95 percent of total units and approximately 80 percent of capacity over the 1920–50 period.

Irrigation Districts

Since the 1950s, there has been a shift away from individuals and partnerships, as well as from groundwater sources. By the 1970s, irrigation districts—public corporations run by local landowners and empowered to tax and issue bonds to purchase or construct, maintain, and operate irrigation works—had become the leading suppliers. The district organization rapidly rose in importance over two periods. In the first, lasting from 1910 to 1930, acreage supplied by irrigation districts increased from one-in-fifteen to approximately one-in-three. Much of this growth came at the expense of cooperative and commercial irrigation enterprises. Between 1930 and 1960, the district share changed little. During the 1960s, the district form experienced a second surge growth, which was due in part to the rising importance of large-scale federal and state projects, which distributed water through these organizations. By 1969, irrigation districts supplied more than 55 percent of all irrigated acreage.

As with so many other areas of California agriculture, success in managing water heavily depended on cooperative action, rather than just individual initiative. Water access has often been contentious, pitting farmers against urban interests and farmers against farmers. Everyone involved attempted to capture government to gain an advantage. Part of the problem is that historically, property rights in water were less well defend than in most private goods and assets, and rights based on location or historic conditions invariably led to inefficient patterns of use.

Adverse Consequences

Moreover, with few restraints on farmers’ use of private pumps, individual farmers have predictably depleted aquifers, leading to deeper and more expensive wells and higher energy costs. In addition, decades of irrigation, along with the use of fertilizers and chemicals to control weeds and pests, have contaminated the soil with salts, selenium, and other chemicals. As one sign of the problem in the 1980s, the drainage of farm water into the Kesterson National Wildlife Refuge, located in the San Joaquin Valley, resulted in widespread birth defects in birds and fish from selenium poisoning. More troubling, many have noted high incidents of environmentally related health problems of agricultural workers. The long-run survival of the current agricultural system is now being questioned. One thing seems certain, especially considering global warming ushering in an era of hotter and more variable climatic conditions: dealing effectively with these problems will require more regulation to preserve aquifers, use water wisely, and limit harmful practices.