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Delta Island Agriculture

Delta Island Agriculture. Technical Workshop on Modeling Issues of the Delta February 6, 2007 Jim Wilde, P.E. Delta Modeling Section California Department of Water Resources wildej@water.ca.gov. Discussion Topics. Delta Island Consumptive Use (DICU) Model description

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Delta Island Agriculture

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  1. Delta Island Agriculture Technical Workshop on Modeling Issues of the Delta February 6, 2007 Jim Wilde, P.E. Delta Modeling Section California Department of Water Resources wildej@water.ca.gov

  2. Discussion Topics • Delta Island Consumptive Use (DICU) • Model description • DICU model results • How does the model do? • DICU uncertainties • What are the inherent model uncertainties

  3. DICU Model Inputs • 142 subareas Some islands contain > 1 subarea • 20 land use types Each type is aggregated for each subarea • 7 precipitation stations Distributed by Thiessen Polygon method • Constant seepage into low lands 0.3 inches per foot of crop root depth per month • Long term average crop consumptive use CU is then adjusted by pan evaporation

  4. DICU Model Outputs Monthly Average: • Diversions • Water taken out of channels • Seepage • Channel loss to the islands • Drains • Return water pumped back to channels

  5. Ag Diversions and Drains

  6. Impact of Ag Use in Dry Periods

  7. DICU Model Uncertainty • Irrigation • Fixed seasons for each crop • Schedule differs for critical and non-critical water year types • Monthly time step reduces variability • Stormwater runoff cannot be estimated • Long term historic land use patterns not used • The land use is assumed constant • Double cropping not considered

  8. DICU Model Uncertainty • Leaching patterns are assumed the same every year • Applied as a post-processing step • CU adjustment from one pan evaporation location • Uncertainty in spatial variability • What are the farmers really doing? • Estimating local water management practices can be challenging at best

  9. Now on to Delta AG Water Quality

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