Date of Graduation
Master of Science in Environmental Management (MSEM)
College of Arts and Sciences
Allison Luengen, PhD
The Pajaro Valley, located along California’s Central Coast, is the State’s 5th most productive agricultural region. Groundwater is the main source of water for the region, and due to high agricultural demand, the Pajaro Valley is facing groundwater depletion and rapid seawater intrusion. Artificial recharge of recycled water into groundwater aquifers in other locations has proven to be an effective method of mitigating groundwater depletion and seawater intrusion while providing a sustainable water supply. Two methods of artificial recharge with recycled water exist: direct injection and surface spreading (infiltration). Case studies of both methods of recharge were analyzed to determine the benefits, issues and solutions associated with each project type. Direct injection is very effective when used as a seawater intrusion barrier to exert hydraulic pressure on seawater, preventing it from flowing inland. As evidenced by several case studies, clogging can be significant in direct injection wells, but well design and maintenance can effectively address clogging. Surface spreading basins require less engineering and have lower operating costs than direct injection, and they are able to accommodate fluctuating flows of water, unlike direct injection wells. Clogging of the infiltration basin surface is inevitable, as demonstrated by the case studies, but this type of clogging is relatively easy to remedy with regular basin maintenance. Based on the information gained from the case studies, the Pajaro Valley is a feasible basin for both direct injection, in the form of a seawater barrier, and surface spreading operations. A dual project featuring both a seawater barrier directly along the coast and a surface spreading basin further inland is recommended to provide the highest possible defense against saltwater intrusion while taking full advantage of all recycled water production to recharge the groundwater aquifer and supplement water supplies.
Heir, Olivia, "Artificial Recharge of Groundwater with Recycled Municipal Wastewater in the Pajaro Valley" (2016). Master's Projects. 344.