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Lecture+11-19-08+CA+Agriculture+_+Water-+Josh -...

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Unformatted text preview: Agricultural Water Management in the Central Valley A Closer Look at the Storage, Use, and Reuse of Water Josh Pollak ES 10 11.19.08 Water and Agriculture: Two Views Comments based on Pacific Institutes' More With Less Report: "...our analysis looks at precisely that: how to grow more food with less water." -Peter Gleick, President, Pacific Institute "... it is easy to see an organization's agenda to grab water from agriculture and dedicate it to the environment." -James O'Banion, Chairman, San Joaquin River Water Authority Outline: Water and Agriculture Why look at water and agriculture in California? What are the current issues? What are some solutions? Storage opportunities Water use efficiency Water re-use Why Look at Ag & Water in California? Productive Ag Sector: 15% of nation's total export, 400 different commodities About half of fresh fruits, nuts, vegetables consumed by Americans 80% of CA water withdrawn is used in ag Almost half of water for ag comes from rivers that once flowed into Delta Endangered Delta smelt & pumping Over 700 native plant and animal species in delta Many depend on sensitive range of salinity Background: California has a Mediterranean Climate Precip. Records for Mt. Shasta 90 80 70 60 50 40 30 20 10 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 High interannual and intra-annual variation in precipitation Societies with this climate respond with storing winter rains & irrigation California has most complex water infrastructure in the world Inches Water Year Farming & California Water More vulnerable than urban users to fluctuations in water supply Agriculture provides jobs (about 4% in state) and about 2% of state's economic output (could be closer to 6%) Farms provide myriad benefits, including: Local food source Backbone of rural economy & lifestyle CO2, habitat, prevents development and more Central Valley Farms & Water Dairies need water for irrigating crops, flushing alleys, and cooling milk Dairies tend to use large amounts of water Water quality problems from: animal waste, fertilizers and pesticides Opportunity for improvement The Current Crisis "Whiskey is for drinking; water is for fighting over" - Mark Twain Statewide drought proclaimed for the first time since 1991 Caused by combination of low rainfall, early melt of snowpack, and courtordered water restrictions 3 main groups battle for water: urban, agricultural, environmental interests Number of looming problems: climate change, vulnerability of Delta, population growth As of August, crop losses totaled $245 million Numerous Potential Solutions But Too Many "Cooks in the Kitchen" Schwarzenegger, Feinstein want to pass more bonds to repair infrastructure System-wide solutions important Too many stakeholders presenting many multi-layered plans CalFed was an attempt to get over 20 Federal and State agencies to work together to solve water problems, failed in its mission Delta Vision and Bay-Delta Conservation Plan are looking at the "big picture," many are hoping they will come out with a tangible plan Management Opportunities Conjunctive Management Conjunctive management Managing groundwater and surface water together Both come from the same sources and are directly linked California has complex water laws Groundwater and surface water are legally considered as separate resources The vast majority of groundwater pumping is unregulated Over time, huge decline in groundwater levels in California Storage Opportunities Groundwater Banking Using natural underground aquifer space to store excess surface water Useful in Mediterranean climate excess water can be diverted in large winter storm events Two types of banking direct recharge, in lieu recharge Only suitable for certain types of geology Storage Opportunities Aquifers in the Central Valley Aquifers can store 13 times surface reservoirs 570 MAF compared to 43 MAF 515 delineated groundwater basins in CA capacity for storage of hundreds of MAF Storage Opportunities Successful Groundwater Banking Projects There are over 20 successful groundwater banking operations Most well-known are Kern Water Bank Authority, Semitropic; both can put/take ~500,000 acre-feet per year Large capital investment needed, but has shown to be profitable Natural Heritage Institute study on groundwater banking projects, concluded that main factors for success are trust, hydrologic benefit, and profitability Water Use Defining Irrigation Efficiency Evapotranspiration is sum of evaporation and transpiration Amount of H2O transpired reaches a maximum Water applied to fields either gets taken up by the plant, percolates into the soil, or runs off the field Irrigation efficiency is the yield per unit of water applied or transpired Some crops (almonds, avocados, grapes) are by nature more efficient users of water, others require more (alfalfa, rice, cotton) Water Use Irrigation Systems, Cost & Efficiency Numerous types of irrigation technology Flood/furrow, sprinkler, microirrigation, subsurface irrigation Irrigation efficiency tends to scale with water availability Generally, more precise irrigation more expensive With water shortages, the trend is towards more technological development GIS, crop models, precision ag, soil maps, soil moisture, weather information CA Irrigation Management Info System (CIMIS), run by DWR Water Use Deficit Irrigation of Alfalfa Deficit irrigation is: Applying little or no water to alfalfa during summer months, when yield is low Transferring water to other users for large profit Alfalfa requires large amounts of water; uses more than any other crop, ~16% of all CA water Essential feedstock for the dairy and beef industries Yields will bounce back in Fall Cost to farmer: $65/acre-foot, profit: $865/acre-foot Water Reuse Tailwater Recovery Collecting water that runs off the field in furrow irrigation systems, and pumping it to other fields Not too expensive, $150-250 per acre Can improve efficiency of system by 25-30% Concerns with build-up of salinity in water Water Reuse Reverse Osmosis INFLUENT SLUDGE Conceptually simple, difficult to implement in practice With farm wastewater, problems include membrane fouling, high power use and cost Numerous developments in materials science, could become more affordable Water Reuse Other Solutions Methane Digesters: provide basic level of treatment, generate energy Coagulation: Electrical and chemical Provides source of nutrients Water Reuse Nutrient Extraction Dairy & other farm wastewater is nutrient rich Nearly all wastewater treatment/water reuse methods produce a sludge byproduct Fertilizer market is a multi-billion dollar industry Important to examine N/P/K ratio Looking Forward... What is the role of technology in solving agricultural problems? What will be the outcome(s) of water struggles? Importance of looking beyond environmental issues when dealing with environmental problems Thanks for listening! Questions? ...
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