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STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS
Citation:
BROOKS, H. BARNARD, J. MCDONNELL, R. COULOMBE, AND C. A. BURDICK. STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS. Presented at International Symposium on Advances in Isotope Hydrology and Its Role in Sustainable Water Resources Management, Vienna, AUSTRIA, May 21 - 25, 2007.
Description:
Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporation, transpiration and stream discharge in a gauged watershed with dry summers and wet winters. Our isotope data indicate that plant and soil water have been affected by evaporation. In contrast, stream water is not evaporated, though discharge rates show diurnal cycles driven by transpiration. We conclude that two separate pools of water are held within the soil. One is a faster moving pool held at relatively weak matric potentials, making it more subject to gravitational transport to streams. The other pool is held more tightly by matric forces, has a longer residence time within the soil, and will more likely be evaporated or taken up by plants.