Runoff generation in a degraded Andean ecosystem: Interaction of vegetation cover and land use

Abstract

Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-)hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/-cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. N 29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation.

Land Use and Land Cover Changes under Climate Uncertainty: Modelling the Impacts on Hydropower Production in Western Africa

“…For instance land use and water areas have higher runoff coefficient due to their low infiltration rate; while the grass land, shrubs and forest areas have low runoff coefficient [36]. The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event [35,37]. One of the paper cited by [35] showed that runoff coefficient of natural vegetation and fallows area, cultivated land and barren land are 13%, 20% and 50% respectively.…”

Interactions between payments for hydrologic services, landowner decisions, and ecohydrological consequences: synergies and disconnection in the cloud forest zone of central Veracruz, Mexico

“…Forest conversion to more intensive forms of land use is often accompanied by soil compaction and degradation, which can reduce infiltration rates and increase rainfall-runoff responses (Molina et al 2007, Zimmermann and Elsenbeer 2009, Bathurst et al 2011, Ghimire et al 2013). At our Veracruz site, despite generally higher topsoil bulk density and much lower saturated hydraulic conductivity under pasture compared to regenerating and mature cloud forests (0.49 ± 0.06, 0.45 ± 0.11, and 0.25 ± 0.17 g cm -3 , and 30 ± 14, 615 ± 690, and 777 ± 931 mm h -1 , respectively) (Muñoz-Villers et al 2015), prevailing rainfall intensities at this elevation rarely exceeded topsoil infiltration capacities to generate flood-producing rates of overland flow (Muñoz-Villers and McDonnell 2013).…”

Analysis of soil moisture condition under different land uses in the arid region of Horqin sandy land, northern China

“…Some studies have shown that plant biomass and productivity increased significantly with increasing soil infiltration rates, which have close relationships with covered vegetation types (Benegas et al, 2014;Finley and Glenn, 2010;Fu et al, 2015;Zhang et al, 2014;Zheng et al, 2015). In addition to types and coverage degrees of vegetation (Cerdà, 1998;Molina et al, 2007), precipitation patterns , antecedent soil water content (Guo et al, 2014) and soil properties (Neris et al, 2012) also play the influential role in the water infiltration process.…”