Modelling hydrologic response to strategic agricultural land repurposing in the Tulare Lake Basin California

Water and land management practices play an important role in sustainable food-security globally, particularly due to the growing population, changing climate, and increasing competition for water resources and agricultural land. Climate change and increased demand for irrigation not only impacts agricultural production but also degrading the environment such as groundwater and surface water depletion, soil degradation, and land subsidence. The growing demand for agricultural production increases competition between limited water and agricultural land resources. Thus, it is likely that the land could be re-allocated or repurposed to reduce the share of water. The impact of climate change and increased demand for water have been given a considerable attention in recent years. However, the scope of this study was to analyze the demand for water with scenarios of strategic agricultural land repurposing under present and future climate change. Changes in policy like Sustainable groundwater management act (SGMA) of 2014 are the major shift in achieving groundwater sustainability in the California. A study motivated from SGMA act projected to lead more than 500,000 acres of agricultural land retirement in the south California basin over next 10-20 years. Land repurposing is likely to happen over the next 10-20 years to achieve groundwater sustainability goals by reducing the demand for irrigation water in the Tulare Lake basin California. This basin is thus an ideal region to examine the land repurposing plans in terms of changing evaporative demand under current and future climate change. This study uses the concept of water balance model using physically based, semi-distributed, Soil Water and Assessment tool (SWAT) in the Tulare Lake basin, California. We have used combinations of strategic land repurposing scenarios based on habitat restoration plans combined with historical land use patterns to reduce water demand in the study region. The purpose of this paper is therefore to examine the following questions: (1) What will be the change in actual evaporation based on existing land cover under present and future climate projections (RCP 4.5 and RCP 8.5) and (2) What will be the change in evaporative demand after adapting land repurposing scenarios under future climate projections (RCP 4.5 and RCP 8.5)? Our results show that reduction in evaporative demand is between 10.32 % to 19.4 % if 214,000-500,000 acres of land retired, as predicted under CMIP5 scenarios, which may considerably offset the groundwater overdraft and help meet the SGMA goals.