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McKnight - 0000-0002-6013-193X
hydrogeology, arid, hydrology
In water-stressed arid basins, questions continue to mount over the compounding impacts of anthropogenic groundwater extraction and climate-driven perturbations on groundwater-surface water interactions and the resulting resilience of ecosystem-critical surface waters. Coupling groundwater and surface water level observations with surface water extents from Sentinel-2 data provides an unprecedented opportunity to evaluate surface water connectivity with local aquifers following intense, sporadic precipitation events in arid basins. Surface water area, surface water level, and groundwater level data were analyzed for trends following precipitation, including peak lag time, post-peak decline rates, and changes in hydraulic gradients. Results indicate variable connectivity following precipitation events between surface water change and groundwater level fluctuations in the upgradient freshwater aquifer with a Pearson correlation of 0.5-0.9, whereas the downgradient brine-to-brackish area of the aquifer indicated virtually no connectivity with the upgradient freshwater aquifer, having a correlation of $$ 0.9), though the log base value of that relationship spatially differs (0.01-0.03). Lumped parameter modeling of surface water inundation also constrains the possible hydrologic dynamics of the post-precipitation response of surface waters. While modeled influx to surface water seems primarily controlled by watershed hydraulics rather than direct hydraulic connectivity of the aquifers, the relationship between surface water and adjacent groundwater levels coupled with surface water area indicate that local aquifers are primarily connected to the surface water bodies through discharge via subsurface infiltration. Modeling results imply that the existence of brine-adjacent surface waters in arid basins are extremely reliant on upgradient discharge from freshwater aquifers despite limited implications for surface water being directly connected hydraulically with local aquifers, and yet that preferential pathways coupled with upgradient spring-fed runoff are a critical physical aspect of recharge to surface waters in arid basins. Our results further support that marginal surface water systems can themselves serve as a critical recharge mechanism to local aquifers.
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McKnight, Sarah; Boutt, David F.; Munk, Lee Ann; and Moran, Brendan, "Data for "Distinct hydrologic pathways regulate perennial surface water dynamics in an arid basin"" (2022). Data and Datasets. 156.