Quantifying and regionalizing land use impacts on catchment response times with high-frequency observations

Abstract

Land use and land cover change (LUCC) can affect the hydrological response time of rivers. However, it is difficult to generate robust and quantitative evidence of this impact at the catchment scale. This lack of evidence also affects the development of rainfall-runoff models to make ex-ante predictions. Here, we analyze high-frequency observational data from a network of pairwise catchments in the tropical Andes and find a statistically significant impact of intensive land use on the hydrological response time, which can be used for regionalization. First, we isolated individual rainfall response events from 5-minute precipitation and discharge time series of 16 catchments (8 pairs). We then fitted unit hydrographs on these events to estimate the catchment response times. These response times were subsequently regionalized by, first, applying a forward stepwise regression to select statistically significant catchment characteristics including land use and land cover, then, fitting a linear mixed-effects model with the selected characteristics to account for within-site variability between pairs. We find that catchments with intensive land use have a significantly quicker response than their natural counterparts. Differences were often sub-hourly, highlighting the value of high-frequency monitoring. Forward stepwise regression identified only catchment area and intensive land use percentage as statistically significant predictors. Model coefficients show that, even when considering other catchment characteristics, increasing intensive land use percentage decreases response times. This study provides solid evidence and a robust methodology to quantify the impacts of LUCC on catchment hydrology