A Calibration Procedure Using Topmodel to Determine Suitability

An evaluation was conducted on three forested upland CT: An evaluation as t land watersheds in the northeastern U.S. to test the suitability of TOPn rtheastern U. t test the suitability of ­ MODEL for predicting water yield over a wide range of climatic L for predicting ater i ld er e tic scenarios. The analysis provides insight of the usefulness of TOPs. ­ MODEL as a predictive tool for future assessments of potential L as ti e l r t r t ti l long-term changes in water yield as a result of changes in global clii ater yield as a result of changes in global cli­ mate. The evaluation was conducted by developing a calibration e l con l ing a alibration procedure to simulate a range of climatic extremes using historical ran e of li temperature, precipitation, and streamfiow records for years hav­ pr , str l rds for years hav­ ing wet, average, and dry precipitation amounts from the Leading i et, a era e, a r reci itati a ts fr t e ea i Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook r ( t d ubbard Brook (New Hampshire) Experimental Watersheds. This strategy was pshire) peri ental atersheds. This strategy as chosen to determine whether the model could be successfully cali­ t r hether the model could be successf ll ­ brated over a broad range of soil moisture conditions with the br ra of s iti ns ith t e assumption that this would be representative of the sensitivity nec­ t this woul t tive f ­ essary to predict changes in streamfiow under a variety of climate t r i str l vari t f change scenarios. The model calibration was limited to a daily time el cali rati as li it to a aily ti e step, yet performed reasonably well for each watershed. Model effi­ t , et performed reasonably we l for each watershed. Model e fi­ ciency, a least squares measure of how well a model performs, aver­ y, l easure of ho ­ aged between 0.64 and 0.78. A simple test of the model whereby . . le l daily temperatures were increased by 1.7CC, resulted in annual were increased by 1.7'C, resulted in l water yield decreases of 4 to 15 percent on the three watersheds. s t Although these results makes the assumption that the model comt t assu ti that the model co ­ ponents adequately describe the system, this version of TOPMOD­ d syste , this version of ­ EL is capable to predict water yield impacts given subtle changes in t ter yiel i acts gi s tle changes in the temperature regime. This suggests that adequate representa­ t t r t r r i . is s sts t t t r r s ta­ tions of the effects of climate change on water yield for regional eff al assessment purposes can be expected using the TOPMODEL conpur ca be expecte using the TOP ­ cept. ce t. (KEY TERMS: model calibration; climate change; forested water­ S: odel calibration; cli ate ge; r sted t ­ sheds; hydrologic modeling; TOPMODEL; water yield.) s s; hy r l i li ; ; ater yield.)