Contour Dataset of the Potentiometric Surfaces of Shallow and Deep Groundwater-Level Altitudes in the Walla Walla River Basin, Oregon and Washington, January–April 2021

This dataset contains manually developed 50-, 100-, and 500-ft contours depicting shallow and deep potentiometric-surface maps for the Walla Walla River Basin aquifer system, Oregon and Washington. The potentiometric surfaces show altitude at the water-table throughout the region (shallow) and at which the water level would have risen in tightly-cased wells beneath the basin-fill deposits (deep). Potentiometric surfaces generally represent synoptic conditions during January–April of 2021. The water-table map was developed using groundwater-level measurements from shallow wells open to the upper part of the unconfined aquifer and the altitudes of springs and gaining stream reaches and constrained by the altitude of the land surface. The deeper potentiometric-surface map was developed using measurements from deeper wells open to basalt beneath the basin-fill sediments. Both maps were also informed by water levels collected before and after the period depicted where these water levels added additional insight, particularly during the drilling process of some of the water-level wells. The hydraulic-head distributions depicted are generalizations. The large study area, availability of water-level measurements, the distribution of wells across the Walla Walla River Basin, and resource limitations precluded mapping all the complexities of the head distribution. Groundwater heads of 1,000 ft or more were mapped using 500-ft contour intervals and generally coincide with upland areas where wells are sparse and the water table is strongly controlled by topography.