Mark D.Tomer and Keith E.Schilling

Journal of Hydrology

Published date September 30, 2009

A simple approach to distinguish land-use and climate-change effects on watershed hydrology

  • States that impacts of climate change on watershed hydrology are subtle compared to cycles of drought and surplus precipitation (PPT), and difficult to separate from effects of land-use change
  • States that, in a 25-yr, small-watershed experiment in Iowa, when annual hydrologic budgets were accrued between droughts, a coupled water-energy budget (ecohydrologic) analysis showed effects of tillage and climate on hydrology could be distinguished
  • An analysis of covariance showed the fraction of precipitation discharged increased, while unsatisfied evaporative demand decreased with time among the four watersheds (p < 0.001)
  • Within watersheds, agricultural changes were associated with ecohydrologic shifts that affected timing and significance, but not direction, of these trends
  • Thus, an ecohydrologic concept derived from small-watershed research, when regionally applied, suggests climate change has increased discharge from Midwest watersheds, especially since the 1970s
  • By inference, climate change has increased susceptibility of nutrients to water transport, exacerbating Gulf of Mexico hypoxia