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Understanding irrigator responses to previous changes in water availability is critical to building effective institutions that allow for efficient and resilient management of water resources in the face of potentially increasing scarcity due to climate change. Using remote sensing data, I examined irrigator responses to seasonal changes in water availability in Idaho's Snake River Plain over the past 33 years. Google Earth Engine's high performance cloud computing and big data processing capabilities were used to compare the performance of three spectral indices, three compositing algorithms and two sensors for 2002 and 2007 for distinguishing between irrigated and non-irrigated parcels. We demonstrate that, on average, the seasonal-maximum algorithm yields a 60% reduction in county scale root mean square error (RMSE) over the accepted single-date approach. We use the best performing classification method, a binary threshold of the seasonal maximum of the Normalized Difference Moisture Index (NDMI), to identify irrigated and non-irrigated lands in Idaho's Snake River Basin for 1984-2016 using Landsat 5-8 data. NDMI of irrigated lands was found to generally increase over time, likely as a result of changes in agricultural practices increasing crop productivity. Furthermore, we find that irrigators with rights to small areas, and those with only surface water rights are more likely to have a major reduction (>25%) in irrigated area and conversely those with a large, groundwater rights are more likely to have major increases (>25%) in the extent of their irrigation.

It is becoming increasingly clear that volatiles, such as H2O, CO2, S, Cl, and F, play a major role in both the formation and evolution of mantle melts, and therefore, also in the formation and evolution of the Earth’s crust. Volatile availability defines where melting is most likely to occur. It also directly drives melting in volcanic arcs associated with subduction zones. Although the body of knowledge surrounding volatile budgets in arc and MORB lavas has grown significantly in recent years, there remains only limited data for hotspots, particularly those that penetrate continental crust. The first part of this study reports volatile data, in concert with major oxide and trace element data, from olivine-hosted melt inclusions in basaltic lavas of the Snake River Plain (SRP) and the Columbia River Basalts (CRB), which are believed to be the surface expressions of the Yellowstone hotspot. Almost all samples analyzed record minimum H2O concentrations in excess of 1 wt%, exceeding the largest values obtained for sub aerial eruptions in Hawaii of 0.8 wt%. The most H2O rich lava in the SRP had 3.3 wt%, and in the Columbia River Basalts (CRB) values reach 4.2 wt% H2O. Furthermore, these highest values are always found in the more primitive melt inclusions, based on major oxide and trace element abundances, indicating that the volatiles are of mantle origin, not artifacts of differentiation in the crust. The last part of this study presents new Sr, Nd and the first Hf isotope data for basalts of the CRB and SRP as well as new 40Ar/39Ar dates to further constrain petrogenesis and eruption history. These data strongly support the conclusion that CRB and SRP lavas have undergone significant interaction with the crust in the area. The result is a revelation that the surface expression of the Yellowstone hotspot may be strongly influenced by the availability of volatiles, particularly H2O, left over from previous subduction events in the region.

The Owyhee Plateau (OWP) is an intermontane basalt plateau located at the nexus of the Snake River Plain (SRP) and Oregon Plateau/High Lava Plains (OP/HLP) volcanic provinces, which has been the locus of nearly continuous basaltic magmatism since 17 Ma. Between 17-11 Ma, generally evolved basaltic lavas related to the Steens flood basalt event and Oregon-Idaho Graben (OIG) volcanism were erupted around the extending margins of the OWP. Beginning 11 Ma, less differentiated olivine tholeiites were erupted throughout the OWP proper, from low shield vents with alignments consistent with regional stress fields. After 5 Ma, volcanism retreated to the margins of the OWP, ultimately becoming limited to the northern transition region between the OWP and the OIG. The youngest basalts in the OWP region are