Climate Change Impacts on Water for Agriculture in California: A Case Study in the Sacramento Valley

This study presents an application of the Water Evaluation and Planning (WEAP) system for California's Sacramento River Basin. The WEAP modeling system was used to evaluate the impact of four future climate scenarios on agricultural water management in the region, and to investigate whether water management adaptation could reduce potential impacts. This paper demonstrates how internalizing adaptation in a model that includes both the hydrologic and water management conditions associated with climate change can help assess potential tradeoffs in multi-objective water management systems.

WEAP is an integrated hydrology/water resources systems model that allows for assessment of climate change impact and adaptation in the water sector based solely on future climate time series. The analysis presents WEAP simulations for each of the climate change scenarios with both adaptation strategies implemented across all agricultural areas of the Sacramento Valley. The modeling of impacts was refined to include adaptation strategies including: 

- improved irrigation efficiency, and

- changes in cropping patterns in response to water supply conditions.

Water supply and delivery projections for the end of the century are provided under conditions where adaptation strategies were employed, and without for regions across Sacramento Valley.

The strategy of adjusting cropping patterns is described "as a function of the evolving status of available water supplies. This adaptation reflects the fact that at the beginning of the growing season, farmers decide which crops to plant based on anticipated surface water supplies and groundwater levels. How farmers respond to these changing conditions is a function of a number of factors, which change depending on the reliability of various available water sources. For example, non-district areas base their cropping decisions solely on the depth to groundwater, because they lack guaranteed surface water supplies."

Overall, the modifications of agricultural water demands from implementing climate adaptation strategies were found to improve the reliability of surface water deliveries for all water users in the basin.

 

 

Publication Date: March 2006

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  • Assessment
  • Case study

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