The Importance of High Resolution Digital Elevation Models for Improved Hydrological Simulations of a Mediterranean Forested Catchment

João Rocha,André Duarte,José Vasques,Ana Quintela,Sérgio Fabres,Beatriz Revilla-Romero,Margarida Silva

doi:10.3390/rs12203287

João Rocha, André Duarte + Show 5 more

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https://doi.org/10.3390/rs12203287

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Abstract

Eco-hydrological models can be used to support effective land management and planning of forest resources. These models require a Digital Elevation Model (DEM), in order to accurately represent the morphological surface and to simulate catchment responses. This is particularly relevant on low altimetry catchments, where a high resolution DEM can result in a more accurate representation of terrain morphology (e.g., slope, flow direction), and therefore a better prediction of hydrological responses. This work intended to use Soil and Water Assessment Tool (SWAT) to assess the influence of DEM resolutions (1 m, 10 m and 30 m) on the accuracy of catchment representations and hydrological responses on a low relief forest catchment with a dry and hot summer Mediterranean climate. The catchment responses were simulated using independent SWAT models built up using three DEMs. These resolutions resulted in marked differences regarding the total number of channels, their length as well as the hierarchy. Model performance was increasingly improved using fine resolutions DEM, revealing a bR2 (0.87, 0.85 and 0.85), NSE (0.84, 0.67 and 0.60) and Pbias (−14.1, −27.0 and −38.7), respectively, for 1 m, 10 m and 30 m resolutions. This translates into a better timing of the flow, improved volume simulation and significantly less underestimation of the flow.

Highlights

Forests play a significant role on the hydrological cycle and have a key importance on ecosystems regulation
There are two major research questions that we intend to address: What is the impact of different digital elevation model (DEM) resolutions on surface representation and watershed properties in a flat area? Is it worthwhile to use very high resolution DEMs to simulate catchment processes and responses in a forest dominated catchment under the influence of Mediterranean climate?
Charrier et al [68] pointed out that the use of very high resolution DEMs could better suit for more realistic watershed delineation, which is true for the 1 m and 10 m resolutions DEMs

Summary

Introduction

Forests play a significant role on the hydrological cycle and have a key importance on ecosystems regulation. In Portugal, forests cover about 36% of the total mainland area [4], holding an important role on the environment and on the national economy. In order to obtain insight on hydrological responses and on water availability at a catchment scale, hydrological models may be used. These models require, as an input, a morphological surface representation, and the digital elevation model (DEM) is one of the most common. DEM is a numeric representation of a surface arranged in a set of regular grids each containing the three-dimensional (3D) (x, y, z) coordinate records [5]. A DEM may be produced based on three arrangements: contour lines (x, y data on equal elevation lines); triangular irregular network (non-overlapped linked triplets of nodes with x, y, z data); or mass points (x, y, z data regularly or irregularly distributed) [6]

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