Water balance backward: Estimation of annual watershed precipitation and its long-term trend with the help of the calibration-free generalized complementary relationship of evaporation

Research output: Contribution to journalArticle

Abstract

Watershed-scale annual evapotranspiration (ET) is routinely estimated by a simplified water balance as the difference in catchment precipitation (P) and stream discharge (Q). With recent developments in ET estimation by the calibration-free generalized complementary relationship, the water balance equation is employed to estimate watershed/basin P at an annual scale as ET + Q on the United States (US) Geological Survey's Hydrologic Unit Code (HUC) 2-and 6-level watersheds over the 1979-2015 period. On the HUC2 level, mean annual PRISM P was estimated with a correlation coefficient (R) of 0.99, relative bias (RB) of zero, root-mean-squared-error (RMSE) of 54 mm yr-1, ratio of standard deviations (RS) of 1.08, and Nash-Sutcliffe efficiency (NSE) of 0.98. On the HUC6 level, R, RS, and NSE hardly changed, RB remained zero, while RMSE increased to 90 mm yr-1. Even the long-term linear trend values were found to be fairly consistent between observed and estimated values with R = 0.97 (0.81), RMSE = 0.63 (1.63) mm yr-1, RS = 0.99 (1.05), NSE = 0.92 (0.59) on the HUC2 and HUC6 (in parentheses) levels. This calibration-free water-balance method demonstrates that annual watershed precipitation can be estimated with an acceptable accuracy from standard atmospheric/radiation and stream discharge data.

Original languageEnglish
Article number1775
JournalWater (Switzerland)
Volume12
Issue number6
DOIs
Publication statusPublished - Jun 1 2020

Keywords

  • Complementary relationship
  • Precipitation estimation
  • Water balance

ASJC Scopus subject areas

  • Biochemistry
  • Geography, Planning and Development
  • Aquatic Science
  • Water Science and Technology

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