Effect of DEM resolution on assessing hydrological connectivity in tropical and semi-arid basins of central Mexico

Abstract

• Relief and vegetation should be considered for DEM resolution selection. • High resolution is needed where heterogeneous and dispersed vegetation is present. • Distance to sinks may explain spatial differences in the index of connectivity. • Results show a balance between accuracy and processing for selecting DEM resolution. • Our findings can be considered for hydrological modelling. Assessment of hydrological connectivity is a valuable tool for water management. It enables various environmental factors related to water-mediated transport of matter and energy within or between elements of a system to be identified and incorporated into hydrological models. The index of connectivity (IC) is widely used to quantify hydrological connectivity; however, it may be influenced by the spatial resolution of the digital elevation model (DEM), which is one of the common inputs, as pixel size modifies some basin parameters. Several DEMs available on open-access platforms, with spatial resolutions from 5 to 30 m (LiDAR, ALOS, MEC, ASTER, SRTM), were compared to identify differences between IC in two basins with contrasting environments (Site 1: steep slope terrain with warm-humid climate, and Site 2: gentle hill slopes with semi-arid climate). Differences in perimeters were analyzed using GLM Repeated Measures ANOVA, while for differences in IC, one-way ANOVA was used. Relationships between IC subtracted maps and basin parameters were explored with classification and regression trees (CART). Basin perimeters and IC varied as a function of DEM resolution, but environmental factors such as relief and land use/cover seemed to influence IC maps. Distance to sinks was one of the variables explaining spatial differences in IC between DEMs. The selection of DEM spatial resolution for hydrological connectivity analysis should be based on the characteristics of the study area, economic and technological issues, and whether the objectives can be met with the available DEM resolution.