Domestic well vulnerability to drought duration and unsustainable groundwater management in California’s Central Valley

Abstract

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and the possibility of longer drought duration under climate change threatens domestic well reliability, yet we lack tools to assess the impact of such events. Here, we leverage 943 469 well completion reports and 20 years of groundwater elevation data to develop a spatially-explicit domestic well failure model covering California's Central Valley. Our model successfully reproduces the spatial distribution of observed domestic well failures during the severe 2012-2016 drought (n = 2027). Next, the impact of longer drought duration (5-8 years) on domestic well failure is evaluated, indicating that if the 2012-2016 drought would have continued into a 6 to 8 year long drought, a total of 4037-5460 to 6538-8056 wells would fail. The same drought duration scenarios with an intervening wet winter in 2017 lead to an average of 498 and 738 fewer well failures. Additionally, we map vulnerable wells at high failure risk and find that they align with clusters of predicted well failures. Lastly, we evaluate how the timing and implementation of different projected groundwater management regimes impact groundwater levels and thus domestic well failure. When historic overdraft persists until 2040, domestic well failures range from 5966 to 10 466 (depending on the historic period considered). When sustainability is achieved progressively between 2020 and 2040, well failures range from 3677 to 6943, and from 1516 to 2513 when groundwater is not allowed to decline after 2020.

California's Central Valley Groundwater Wells Run Dry During Recent Drought

“…Because we analyze elevations of well bottoms rather than the top of perforated intervals (see section ), we likely underestimate the abundance of wells that have run dry. The ability to pump water from a well can be impaired before the water table declines below the bottom of the well (Gailey et al, ; Pauloo et al, ). Wells may run dry even when water tables overlie well bottoms for two reasons.…”

Identifying Agricultural Managed Aquifer Recharge Locations to Benefit Drinking Water Supply in Rural Communities

“…Depth to the groundwater table and estimated z t values were used to quantify changes in well status between Spring of 2011 (highest groundwater table before the 2012–2016 drought) and Fall of 2015 (lowest groundwater table during the 2012–2016 drought). Groundwater depths at each well location were extracted from interpolated seasonal groundwater levels spanning the entire shallow to semi‐confined CV aquifer system (Pauloo et al., 2020). To calibrate the required submergence value, h s , z t values were compared to predrought (Spring 2011) and postdrought (Fall 2015) groundwater levels to identify wells that became inactive as a result of groundwater level declines.…”

“…In California’s Central Valley (CV), one of the most productive agricultural regions in the world, agricultural water use (Hanak & Lund, 2012) and climate‐induced reduction of surface water supplies (Diffenbaugh et al., 2015) have led to severe groundwater overdraft in the past century. This has diminished access to clean, reliable drinking water in rural communities (Francis & Firestone, 2010; Pauloo et al., 2020). This unsustainable and inequitable regional change (Francis & Firestone, 2010) has disproportionately impacted disadvantaged communities (DACs), who provide most of the farm labor to the agricultural sector (Howitt et al., 2014), and perpetually decreased the economic viability and resilience of these communities to face hydro‐climatic change (Huang & London, 2012; London et al., 2013; Moore et al., 2011).…”

Energy and water co-benefits from covering canals with solar panels

“…In addition to avoided water costs, the benefits of water conservation from over-canal solar arrays could add resilience to agricultural production. For instance, the conserved water could potentially reduce the amount of ground-water pumping and the practice of field fallowing in response to surfacewater deficits [49][50][51] . While we assume that the rights to the water saved by over-canal projects would follow the complex hierarchy administered by the California State Water Board 52 , it is unclear if these water savings would have an effect on agricultural producers most impacted by surface-water deficits (i.e.…”