A 4‐yr study was conducted to assess the impact of reuse water on soil salinization of nine golf courses in southern Nevada: three long‐term reuse courses, three fresh‐water courses, and three courses that transitioned to reuse water during the experimental period. Four of nine fairways had positive leaching fractions (LFs) during all 4 yr, with statistical separation occurring based on 4‐yr averages (p < 0.001). Soil salinity levels followed a sinusoidal seasonal curve, with 70% of all peaks associated with summer months. Salinity contour maps (surface soil) were compared over time. More than 85% of the surface area of greens were mapped as electrical conductivity of saturation extract (ECe) < 4.0 dS m−1, whereas 64% of the fairways were mapped at ECe < 4.0 dS m−1. This salinity relationship dropped to 13% on fairways of long‐term reuse courses. Changes in the average ECe values after transition to reuse water were primarily driven by the number of days a course had been irrigated with reuse water (R2 = 0.69∗∗∗). Depth‐averaged salinity (sensors) was found to be highly correlated with LF on reuse courses (R2 = 0.86∗∗∗) and transitional courses (R2 = 0.87∗∗∗). Yearly changes in depth‐averaged sensor values on transitional courses were described by an equation that included the number of days a golf course was irrigated with reuse water, the LF, and the uniformity of the irrigation system (R2 = 0.83∗∗∗). Although deficit irrigating can be practiced for short periods, adequate LFs are essential for the long‐term success of golf courses irrigated with reuse water.

The ability to evaluate accurately the response of the environment to climate change ideally involves long‐term continuous in situ measurements of climate and landscape processes. This is the goal of the Nevada Climate‐Ecohydrology Assessment Network (NevCAN), a novel system of permanent monitoring stations located across elevational and latitudinal gradients within the Great Basin hydrographic region (Figure 1). NevCAN was designed, first, to quantify the daily, seasonal, and interannual variability in climate that occurs from basin valleys to mountain tops of the Great Basin in the arid southwest of the United States; second, to relate the temporal patterns of ecohydrologic response to climate occurring within each of the major ecosystems that compose the Great Basin; and, last, to monitor changes in climate that modulate water availability, sequestration of carbon, and conservation of biological diversity.

In this study, evapotranspiration (ET) was estimated for three valleys (White River, Spring Valley and Snake Valley) in the Great Basin region of Nevada (USA) during a 3-year period. ET estimates were based on an energy balance approach using the eddy covariance (EC) method and were scaled to the basin level by developing empirical relationships between ET and remotely sensed spectral data (Landsat). Annual EC-ET values for the three basins and previously published values attained for the same valleys during the same time period were correlated to average normalized difference vegetation index (NDVI) values for the growing period. Resulting empirical relationships accounted for 97% (p < 0Ð001) of the variation in the EC-ET estimate for the 10 May-5 September growing period, and 93% (p < 0Ð001) of the variation in the EC-ET estimates based on measured or projected yearly ET totals.Variations in yearly ET estimates at the different shrubland sites ranged from 20 to 50 cm during the two dry years (2006 and 2007, not including the irrigated site). Winter precipitation was shown to be a significant driving force in the physiological response of the plants and the yearly ET totals. In the case of White River Valley, the ratio of winter precipitation to reference evapotranspiration (ET ref ) declined from 79 to 11% over the 3-year monitoring period. Overall, ET rates in 2007 (May-Sept.) were highly correlated with the percentage cover of greasewood at the monitoring sites (R 2 D 0Ð96 ŁŁŁ ), regardless of the depth to groundwater.

This study investigated near surface hydrologic processes and plant response over a 1600 m mountain-valley gradient located in the Great Basin of North America (Nevada, U.S.A.) as part of a long-term climate assessment study. The goal was to assess shifts in precipitation, soil water status and associated drainage with elevation and how this influenced evapotranspiration and plant cover/health estimated by a satellite-derived Normalized Difference Vegetation Index (NDVI), all to better understand how water is partitioned in a mountain valley system. Data were acquired during a three-year period from meteorological stations located in five plant communities ranging in elevation from 1756 m (salt desert shrubland zone) to 3355 m (subalpine zone). The analysis also included groundwater depths measured at the Salt Desert Shrub West site, mine water flow near the Pinyon-Juniper West site and drainage estimates using drainage flux meters at the four higher elevation sites. Annual precipitation increased with elevation in a linear fashion (R 2 = 0.93, p < 0.001) with an average increase of 2.9 cm for every 100 m in elevation. Reference evapotranspiration (ET ref) declined in a highly linear fashion with elevation (R 2 = 0.95, p < 0.001) with an average 4.0 cm decline for every 100 m rise in elevation. Drainage occurred only at the Montane West and Subalpine West sites and not at the lower elevations. No drainage occurred after Julian day 160. Growing degree days were found to be negatively associated with the time of peak drainage (R 2 = 0.97, p < 0.001), the date drainage first occurred (R 2 = 0.90, p < 0.001), drainage duration (R 2 = 0.79, p < 0.001) and total drainage volume (R 2 = 0.59, p < 0.001). It was estimated that 27% of precipitation at the Montane West site (years 1, 2 and 3) and 66 % at the Subalpine West site (40% without year 1) contributed to drainage at the local site level, indicating possible strong recharge contribution from the higher elevation plant communities. Percent vegetation cover and ET ref accounted for 94% of the variation in NDVI and 90% of the variation in ET totals when data from all sites were combined. Such data will be extremely valuable to collect and compare over time to assess shifts associated with potential climate warming and/or basin water diversion.

Groundwater in remote valleys of the Great Basin (NV, USA) has been approved by the State Engineer for pumping and export. Deep rooted shrubs such as greasewood (Sarcobatus vermiculatus) are partially dependent on this groundwater to meet plant water needs. To assess the impact of a falling water table on greasewood, we monitored evapotranspiration, reference evapotranspiration and precipitation, along with daily groundwater levels for 6·2 years. Groundwater levels declined 130 cm in a highly linear fashion (p < 0·001) over this period. Groundwater oscillations ceased in 2007 followed by a 2225-day quiescent period but then returned to daily oscillations late in 2013 for a 32-day period. The oscillation signature in 2013 coincided with the water level transitioning from sediment with 89% sand to a new horizon with only 8% sand. In 2013, we detected a soil water content depression at both 800 and 900 cm starting in early May that lasted 137 days, ending prior to the groundwater oscillation period when significant rainfall occurred in late August and early September. Soil water storage increase in the surface zone during the active growing period of 2013 was highly correlated (R 2 = 0·77, p < 0·001) to changes in the lower unsaturated zone, suggesting a link between soil water storage zones based on precipitation and plant water extraction. Although the water table declined below 10·7 m and groundwater decoupling did not occur, the current rate of decline driven solely by groundwater pumping for the irrigation of alfalfa fields would suggest extensive pumping for diversion outside of the basin would not be sustainable with regard to maintaining healthy greasewood plants that have a finite rooting depth.