THIRTY-SEVEN YEARS OF EXPERIENCE WITH DETERMINING SUSTAINABLE YIELDS OF HARDROCK WELLS IN THE SIERRA NEVADA
Water-level recovery is extremely important for hardrock well pump tests. Hardrock wells vary greatly in the duration required for full recovery, following the cessation of pumping. Water levels in some wells fully recover within only a few hours. Water levels in other hardrock wells only recover after winter precipitation. Lastly, water levels in some hardrock wells take years or longer to fully recover after a pump test, and yields of these wells are not sustainable.
Available recharge should be considered. Precipitation, plant evapotranspiration, and runoff are key parts of the water budget in undeveloped areas. In low elevation, low rainfall areas, there is little runoff, and only small amounts of groundwater can usually be developed. In contrast, at higher elevations there is much more precipitation and runoff, and more groundwater can generally be developed. One of the most important factors is the size of the tributary watershed, which depends highly on the depths of water-producing fractures tapped by the wells. In general, the deeper these fractures, the larger the tributary area that the wells may draw from.