Abstract
Two methods that define the point of baseflow recession onset were compared using storm hydrograph data for 27 storm events that occurred between 1982-1995 in the Upeo watershed located in the Andes mountain range in central Chile (Figure 1). Three well-known baseflow recession equations were used to determine whether the method we are proposing here, that defines baseflow recession onset as the third inflection point on the logarithmic graph of the falling limb of the storm hydrograph, more accurately models observed data than the most widely used method that defines baseflow onset as the second inflection point on the same graph. Five time intervals were used to modify the recession coefficient in search of a more accurate fit. Results from the coefficient of determination, standard error, Mann-Whitney U test, and Bland-Altman test suggest that redefining baseflow recession onset via the proposed approach more accurately models baseflow recession behavior.
Highlights
Predicting the rate of baseflow recession is important to water resource management for areas with Mediterranean climates; as the rate of baseflow decrease varies little year to year in regions with an extended dry season, recession flow analyses are used to study groundwater systems [1], whose characteristics largely determine the feasibility of land use where options are limited by the availability of water resources (Ponce, 1989).As direct runoff and baseflow recede at different rates, it is required to model them separately; hydrologists often use surface and subsurface flow models to accomplish such an objective [2]
Two methods that define the point of baseflow recession onset were compared using storm hydrograph data for 27 storm events that occurred between 1982-1995 in the Upeo watershed located in the Andes mountain range in central Chile (Figure 1)
Three well-known baseflow recession equations were used to determine whether the method we are proposing here, that defines baseflow recession onset as the third inflection point on the logarithmic graph of the falling limb of the storm hydrograph, more accurately models observed data than the most widely used method that defines baseflow onset as the second inflection point on the same graph
Summary
As direct runoff and baseflow recede at different rates, it is required to model them separately; hydrologists often use surface and subsurface flow models to accomplish such an objective [2]. Baseflow recession models are used to portray the behavior of baseflow and determine minimum water yields and depletion rates [6]. Despite their importance, there are several viewpoints on the effectiveness of baseflow recession models, which often do not accurately model observed data. Vogel and Kroll [8] tested six estimators of the baseflow recession constant derived from data for thousands of recession hydrographs pertaining to 23 sites in Massachusetts, in the process highlighting how certain assumptions made regarding model error structure affected model accuracy
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