Mountain Valley Eco-Hydrologic Connectivity in the Great Basin, NV

Mountain valley systems exist in the Great Basin and extensively throughout state of NV. We undertook field research to assess the eco-hydrologic connectivity between sites on the floor of Spring Valley (desert mixed shrubland plant community and sage brush at the base of the Snake mountain Range) to three additional sites located on the western slope of the Snake Mountain Range, ending at a sub alpine site that contained bristle cone pine at an elevation of 3355 m. Each site had a 10 m tower which could be accessed remotely to obtain atmospheric and soil based data. We report on data collected over a 3 year period that also included a unique data set of drainage flux meter values, mine flow from an abandoned mine, groundwater depths and remotely sensed normalized difference vegetation index values during the growing period. Precipitation and reference evapotranspiration were found to be inversely related over the elevation gradient (R2=0.86, p<0.001). Grow degree days decreased with elevation with 80% of precipitation occurring during the growing period at the montane site compared to only 50% at the subalpine site. Drainage occurred only at the two highest elevation sites, all drainage occurred during periods ranging from 7 to 50 days, occurring on a daily basis during the drainage period and were all completed by day 160. Drainage occurred prior to increased flow from an abandoned mine at an elevation of 2411 m within the Pinyon Juniper plant community. Mine flow peaked after groundwater levels at the mixed desert scrubland site peaked in June of each year. A fundamental relationship existed between annual mine flow discharge, groundwater peak levels and total drainage from the flux meters at the two highest elevations. The growing period as assessed by GDD was found to negatively impact the day associated with peak drainage, day drainage first occurred, drainage duration and total drainage volume (p<0.001). We will discuss these findings along with plant level assessments of % cover, NDVI and evapotranspiration.