Recharge Investigations for the Central Valley Conjunctive Water Use Study

OVERVIEW

The Tulare Irrigation District (TID) provides surface water for 70,000 acres of agricultural land within California’s Central Valley. Under SGMA, providers are required to develop Groundwater Sustainability Plans (GSPs) that outline management policies and practices. One method for promoting sustainability is to optimize the storage of surplus surface water supplies, which are sporadic and often limited in the Central Valley, a condition that has been exacerbated in recent years by drought. This practice will help replenish aquifers and mitigate pumping impacts.

SERVICES

M&A led a hydrogeologic investigation that was part of a conjunctive water use study. The goal of this work was to identify opportunities for increasing recharge capacity and for maximizing the use and storage of seasonal surface water deliveries. Our services included:

• Evaluating TID’s irrigation system and recharge basin distribution
• Coordinating with TID to prioritize basins for field investigations based on limited lithologic data and funding — a task that required a flexible, adaptive approach
• Implementing a trenching program to characterize near-surface lithologic conditions in five basins and to identify sediments / strata that control infiltration rates
• Conducting an exploration drilling program to characterize lithologic and stratigraphic conditions in three basins to a depth of 50 feet
• Identifying potential perching layers and zones with favorable infiltration capacity
• Conducting basin-wide infiltration tests after surface water deliveries began, using TID staff, to document operational infiltration rates under current conditions
• Analyzing results of the exploration trenching, drilling, and testing to determine the limitations to infiltration rates and to develop strategies for increasing the overall recharge capacity within the District

photo credit: The California Department of Water Resources