Abstract
This paper provides a chronology and overview of events and policy initiatives aimed at addressing irrigation sustainability issues in the San Joaquin River Basin (SJRB) of California. Although the SJRB was selected in this case study, many of the same resource management issues are being played out in arid, agricultural regions around the world. The first part of this paper provides an introduction to some of the early issues impacting the expansion of irrigated agriculture primarily on the west side of the San Joaquin Valley and the policy and capital investments that were used to address salinity impairments to the use of the San Joaquin River (SJR) as an irrigation water supply. Irrigated agriculture requires large quantities of water if it is to be sustained, as well as supply water of adequate quality for the crop being grown. The second part of the paper addresses these supply issues and a period of excessive groundwater pumping that resulted in widespread land subsidence. A joint federal and state policy response that resulted in the facilities to import Delta water provided a remedy that lasted almost 50 years until the Sustainable Groundwater Management Act of 2014 was passed in the legislature to address a recurrence of the same issue. The paper describes the current state of basin-scale simulation modeling that many areas, including California, are using to craft a future sustainable groundwater resource management policy. The third section of the paper deals with unique water quality issues that arose in connection with the selenium crisis at Kesterson Reservoir and the significant threats to irrigation sustainability on the west side of the San Joaquin Valley that followed. The eventual policy response to this crisis was incremental, spanning two decades of University of California-led research programs focused on finding permanent solutions to the salt and selenium contamination problems constraining irrigated agriculture, primarily on the west side. Arid-zone agricultural drainage-induced water quality problems are becoming more ubiquitous worldwide. One policy approach that found traction in California is an innovative variant on the traditional Total Maximum Daily Load (TMDL) approach to salinity regulation, which has features in common with a scheme in Australia’s Hunter River Basin. The paper describes the real-time salinity management (RTSM) concept, which is geared to improving coordination of west side agricultural and wetland exports of salt load with east side tributary reservoir release flows to improve compliance with river salinity objectives. RTSM is a concept that requires access to continuous flow and electrical conductivity data from sensor networks located along the San Joaquin River and its major tributaries and a simulation model-based decision support designed to make salt load assimilative capacity forecasts. Web-based information dissemination and data sharing innovations are described with an emphasis on experience with stakeholder engagement and participation. The last decade has seen wide-scale, global deployment of similar technologies for enhancing irrigation agriculture productivity and protecting environmental resources.
Highlights
Irrigation Development on the West Side of the San Joaquin ValleyIrrigated agriculture development on the west side of the San Joaquin Valley (SJV) of California dates back to the middle nineteenth century, fueled by the California gold rush and the policy aims of the federal government to open up the western United States to economic development
This paper focused on irrigation sustainability of agriculture on the west side of the SJV and the San Joaquin River; the San Joaquin (River) Basin (SJRB)—the west side of the SJRB is that subregion within the SJV that drains to the San Joaquin River (SJR) and, to the Sacramento–San Joaquin Delta and San Francisco Bay
The SJRB is an exemplar of the conflicts that occur around the world between agricultural, urban/municipal, and environmental users of scarce water supply and, is well suited for an exploration of evolving policy interventions and how these options have led to the desired level of environmental protection
Summary
In the 1960s federal and state agency determination to arrest land subsidence and offset rising pumping costs led to a joint project to import surface water supply from the Sacramento–San Joaquin Delta to the south through the federal pumping plant of the Central Valley Project (CVP) located at Tracy. A significant case in point was the recent detailed comparison of two integrated regional surface-groundwater hydrologic models [15,16], the USGS Central Valley Hydrologic Model (CVHM) [6] and the state’s Central Valley Simulation Model (C2VSIM) [17] These agency models, which were developed as basin-scale planning tools covering the entire Central Valley (Figure 4), were those suggested by SGMA management as essential, publicly available tools for GSA analysis and GSP formulation purposes. Additional questions have arisen related to the limitations of these model tools to guide sustainable groundwater pumping decisions, which suggests agency inertia in the adoption of newer and technically advanced techniques for the development of crop water budgets and crop evapotranspiration—the major water loss term in the hydrologic budgets Techniques utilized by both models make use of estimates of potential crop evapotranspiration and crop coefficients, most of which come from handbooks and field data collected in the 1970s. Updating existing surface and groundwater hydrology models to take advantage of this new technology will likely resolve the more important technical issues that are constraining the use of these models for long-term resource sustainability planning and allow their eventual use for basin-scale salinity management
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