Land-use changes in the periurban interface: Hydrologic consequences on a flatland-watershed scale

Abstract

The aim of this work was to analyze the hydrologic effects on surface runoff and infiltration of changes in land use and land coverage. The periurban-flatland watershed of El Pescado Creek (Argentina) was the study site investigated. We used Geographic-Information-System techniques together with the curve-number method (CN) to estimate the surface runoff in five land-use scenarios having increasing levels of anthropic impact (years 1986, 1996, 2006, 2016, and 2026) considering two rainfalls and the antecedent-runoff conditions (ARC) defined by that methodology. We identified three hydrologic-soil Groups (B, C, and D) and five land uses (grassland, forest, urbanization, greenhouses, and poultry farms). Land use and land coverage change process increased CN values, and consequently the estimated surface runoff, especially in the upper watershed. Changes towards impervious (687 ha with greenhouses and poultry farms) or semi-impervious land coverage (800 ha with urbanizations) affected infiltration. The most contrasting results were related to the ARC I, II, and III weighted-average infiltration of the watershed that diminished from above 93.0%, down to 88.5% and finally to 50.4%, respectively (calculated with data from the 55.8-mm rainfall), and from 86.6%, to 58.3%, and to finally 28.8% (calculated with data from the 117.8 mm rainfall). Simulating a near-future land-use scenario (year 2026) enabled us to estimate the watershed pattern by adding new area containing semi-impervious and impervious land coverage. The estimated weighted-average infiltrations (ARC II) were 81.3% and 54.9%, for the above 55.8-mm and 117.8-mm rainfalls, respectively. Changes concerning infiltration might be disturbing the natural recharging process of aquifers, carrying out modifications in the hydrodynamics of the watershed, and also affecting water supply for human activities in the territory.