According to its executive summary, the report "is a thorough review of published research and technical data as well as State of California publications to assess the overall potential for agricultural water use efficiency to provide new water supplies. The report found that little potential exists for new water unless large swaths of agricultural land are taken out of production, which technically is not water use efficiency." The report later explains that enhanced agricultural water conservation will never result in sufficient new water to solve the problems of water management or at least provide the volumes of water desired by all users in California.
The key findings of the report include:
- The estimated potential new water from agricultural water use efficiency is 1.3 percent of the current amount used by the state’s farmers – about 330,000 acre-feet per year (at funding level PL-5 of the Department of Water Resources latest California Water Plan Update 2009). That represents about 0.5 percent of California’s total water use of 62.66 million acre-feet.
- Groundwater overdraft of about 2 million acre-feet per year continues to be a serious problem in certain regions of California because of inconsistent and uncertain surface water supplies.
- Changes in irrigation practices, such as switching from flood irrigation to drip, have the effect of rerouting flows within a region (or basin) but generally do not create new water outside of the basin.
- Previous reallocations of agricultural water supplies for environmental purposes represent at least 5 percent of farm water diversions depending on water year.
- On-farm water conservation efforts can affect downstream water distribution patterns, with potential impacts on plants and animals, recreation, as well as human and industrial consumptive uses. The effects can be positive or negative and also inconsistent (e.g., on-farm conservation could reduce a city’s water supply but improve the nonpoint source situation).