Monday, June 21, 2010

Running on Empty III

The winter rains have brought a reprieve from the recent water crisis in California, but this is not a solution. The federal government has upped the water allocation from the federal pipes and canals to the Central Valley to 45% of the “total allocation” from the previous 5%. As politicians who lobbied the Department of the Interior to raise the allocations and boost irrigation supplies take credit for the increase brought by the winter rains in this election year, addressing the underlying problem is pushed down the road. California will issue $11 billon in bond money they do not have to repair the San Joaquin- Sacramento Delta, water projects and build dams to try and magically increase the supply of water. Dams will not solve the problem of not enough water to meet demand, but may add to the growing insolvency of the state. Including interest payments, the bonds will cost $24 billion out of the general fund over 30 years. The general fund has a current deficit of $19 billion this year. If the legislature feels all these provisions are necessary then they should directly raise water rates to pay for the costs.

California local water agencies have invested in water recycling, conservation, groundwater storage and other strategies to stretch supplies, but the demand for cheap water exceeds supply as evidenced by the groundwater usage. Year round agriculture has been made possible by the ample supply of water used for irrigation. The limit to California’s agricultural bounty is water availability. Water available is a combination of surface water diversions and groundwater pumping. In 2006 before the beginning of the last drought, California used almost 31 billion gallons of water a day for irrigation. This is 351 gallons of water a day for each agricultural dollar earned each year and represents 80% of the water used in the state each year. Buried in the water bond legislation contains a provision that would require most California communities to reduce their per capita water use 20% by 2020. That is a little like China agreeing to reduce their carbon intensity. The total water used will grow with the population, but there will be no growth in the water supply for the state and if climate projects are at all true, then there will be less water.

While a portion of irrigated water is recharged to groundwater and surface water, some is lost; the real problem is that there is inadequate water flow in the state to support this level of irrigation. Period. When California reduces the irrigation allocations, the agricultural use of groundwater increases. Many agricultural operations do not have adequate ground water flow to make up the shortage, resulting in loss of jobs and crops. The operations with available groundwater utilize it without regard for the recharge rate and ultimate impact on California’s future. When you withdraw the groundwater from fine-grained compressible confining beds of sediments and do not replace it, the land subsides. The incredibly fertile Central Valley was identified by the research efforts of Joseph Poland as the location of maximum subsidence in the United States. Once the land subsides, it looses its water holding capacity and will never recover as an aquifer. Groundwater mining in the Central Valley had slowed in the past few decades, at least until the recent water crisis.

California’s climate is dominated by the Pacific storm track. The mountain ranges cause precipitation to fall mostly on the western slopes. These storms also leave tremendous accumulations of snow in the Sierra Nevada during a wet winter. While the average annual precipitation in California is about 23inches (DWR 1998), the range of annual rainfall varies greatly from more than 140 inches in the northwestern part of the State to less than 4 inches in the southeastern part of the State. Snowmelt and rain fall in the mountains and flow into creeks, streams, and rivers. As these flows make their way into the valleys, much of the water percolates into the ground. The vast majority of California’s accessible groundwater is stored in alluvial groundwater basins. Though the health of the groundwater basins is neither tracked nor known, it is believed that California may be using the groundwater at an unsustainable rate.

California’s water allocations exceed supply in practically every year of recent record. Climatic variability produces both droughts and flooding. California has dealt with the limitations resulting from its natural hydrology by developing an intricate system of reservoirs, canals, and pipelines under federal, State and local projects to essentially move the water from the northwest to the south. However, a significant portion of California’s water supply need is always met by groundwater. Typically, groundwater supplies about 30 percent of California’s urban and agricultural uses. In dry years, groundwater use increases to about 40 percent statewide and 60% or more in some regions. Mining of the groundwater beyond the recharge rate is impairing California’s future. California does not have enough water available annually to keep up this usage level and the largest user of water in the state is agriculture. In order to continue to supply water to the rest of the state, California needs to reduce the agricultural water usage in the state.

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