Getting water right: A case study in water yield modelling based on precipitation data.

PESSACG. N.; FLAHERTY, S.; BRANDIZI, L.; SOLMAN, S.; PASCUAL, M.A.

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 537 p. 225 - 234

0048-9697

Water yield is a key ecosystemservice in river basins and especially in dry regions around theWorld. In this studywe carry out a modelling analysis ofwater yields in the Chubut River basin, located in one of the driest districts ofPatagonia, Argentina. We focus on the uncertainty around precipitation data, a driver of paramount importanceforwater yield. The objectives of this study are to: i) explore the spatial and numeric differences among sixwidelyused global precipitation datasets for this region, ii) test them against data from independent ground stations,and iii) explore the effects of precipitation data uncertainty on simulations of water yield. The simulations wereperformed using the ecosystem services model InVEST (Integrated Valuation of Ecosystem Services andTradeoffs) with each of the six different precipitation datasets as input. Our results show marked differencesamong datasets for the Chubut watershed region, both in the magnitude of precipitations and their spatialarrangement. Five of the precipitation databases overestimate the precipitation over the basin by 50% or more,particularly over the more humid western range.Meanwhile, the remaining dataset (Tropical Rainfall MeasuringMission ? TRMM), based on satellite measurements, adjusts well to the observed rainfall in different stationsthroughout the watershed and provides a better representation of the precipitation gradient characteristic ofthe rain shadow of the Andes. The observed differences among datasets in the representation of the rainfallgradient translate into large differences in water yield simulations. Errors in precipitation of+30% (−30%) amplifyto water yield errors ranging from 50 to 150% (−45 to −60%) in some sub-basins. These results highlightthe importance of assessing uncertainties in main input data when quantifying and mapping ecosystem serviceswith biophysical models and cautions about the undisputed use of global environmental datasets