QUANTIFYING HYDROLOGIC BUDGET COMPONENTS IN INDIANA USING A NETWORK OF METEOROLOGICAL AND VADOSE-ZONE INSTRUMENT ARRAYS

Weather stations in the United States that collect reliable, long-term meteorological data sets are now widely distributed owing to advances in both instrumentation and remote data-server technology. However, with the exception of Illinois, sites collecting soil-moisture and soil-temperature data remain sparse in the Midwest, and fewer locations exist where complete meteorological data are collected along with vadose-zone data. Coupled monitoring networks are important for establishing reliable land surface water and energy budgets and estimating deep drainage in the soil profile. They also provide essential data for expanding our understanding of soil moisture-climate coupling.

Accordingly, a network of 11 monitoring stations has been developed in Indiana. Nine of the stations are located in glaciated environments including: ground moraine, moraine crest, outwash terrace, and alluvial terrace settings with the remaining two sites situated in reclaimed-mine and unglaciated highland settings. Each instrument array employs standard meteorological sensors, including pyranometers used to measure incoming shortwave solar radiation at seven of the sites and net radiometers at four of the sites. The resulting data are used to calculate potential evapotranspiration (PET) using standard methods by the Food and Agriculture Organization (FAO) of the United Nations. Vadose-zone instrumentation is installed at six of the glaciated sites and includes time-domain reflectometry soil-moisture and temperature sensors at 0.3-m depth intervals down to a depth of 1.8 m, in addition to matric-potential sensors at 0.15, 0.3, 0.6, and 1.2 m. Shallow water-table aquifers are present at three of the sites, and piezometers are used to measure water-table fluctuations.

Beyond providing PET estimates using the FAO guidelines, the data will be used to determine groundwater recharge using the soil-water-balance approach. The significance of quantifying these hydrosphere components is especially important with more frequent drought conditions creating increasing stresses on groundwater resources and agriculture in Indiana. Future land-based modeling efforts aimed at improving our understanding of soil-moisture and recharge distribution will also benefit from having an established empirical data network.