Challenge: To develop a decision support planning tool and identify conjunctive use projects to reduce water demand and supply gaps and enhance drought resiliency. 

Solution: INTERA developed a decision-support framework to support long range planning and completed a feasibility study of conjunctive use projects in the El Monte and Moreno groundwater sub-basins within the San Diego River Basin. Hydrologic records (precipitation and groundwater levels) as well as operational records from several surface water reservoirs were used to develop analytical relationships for groundwater storage, natural recharge from the river, recharge from reservoir releases, and managed recharge/extraction capacities. We then updated and used a dynamic simulation model of San Diego's surface-water, groundwater, and conveyance systems to analyze local and imported water supply storage and transfer between any of these storage facilities to minimize spills and evaporative losses and maximize overall water storage opportunities under multiple demand and supply scenarios. Long term projections for local and imported water supplies, as well as water demands under baseline and climate-change impacted conditions, were also incorporated into the analyses. 

Results: INTERA identified several viable conjunctive use projects that offer the potential to improve long-term water supply reliability. More detailed evaluations of the costs and benefits of these alternatives are currently underway.