Groundwater is increasingly important for satisfying California’s growing fresh water demand. Strategies like managed aquifer recharge (MAR) can improve groundwater supplies, mitigating the negative consequences of persistent groundwater overdraft. Distributed stormwater collection (DSC) MAR projects collect and infiltrate excess hillslope runoff before it reaches a stream, focusing on 40–400 ha drainage areas (100–1000 ac). We present results from six years of DSC–MAR operation—including high resolution analyses of precipitation, runoff generation, infiltration, and sediment transport—and discuss their implications for regional resource management. This project generated significant water supply benefit over six years, including an extended regional drought, collecting and infiltrating 5.3 × 105 m3 (426 ac-ft). Runoff generation was highly sensitive to sub-daily storm frequency, duration, and intensity, and a single intense storm often accounted for a large fraction of annual runoff. Observed infiltration rates varied widely in space and time. The basin-average infiltration rate during storms was 1–3 m/d, with point-specific rates up to 8 m/d. Despite efforts to limit sediment load, 8.2 × 105 kg of fine-grained sediment accumulated in the infiltration basin over three years, likely reducing soil infiltration capacity. Periodic removal of accumulated material, better source control, and/or improved sediment detention could mitigate this effect in the future. Regional soil analyses can maximize DSC–MAR benefits by identifying high-infiltration-capacity features and characterizing upland sediment sources. A regional network of DSC–MAR projects could increase groundwater supplies, while contributing to improved groundwater quality, flood mitigation, and stakeholder engagement.

This dataset contains six years of monitoring data from a managed aquifer recharge system that collects stormwater runoff. Runoff from a drainage area of 173 acres is diverted into a 4.3-acre infiltration basin. There is a small sediment detention basin that the runoff passes through before reaching the infiltration basin. This dataset includes: - Raw precipitation records from the field site and daily precipitation records - Calculations of daily runoff collected (measured as flow rate through a culvert feeding the infiltration basin) - Mass balance calculations to estimate the average daily infiltration rate - Field measurements of sediment accumulation throughout the basin - Survey of the field site (requires the program Surfer to open) - Grain size data from hundreds of sediment samples collected from throughout the system - Estimations of daily vertical infiltration rate at three points in the infiltration basin These data are part of a study that was published in Journal of Environmental Management.