Abstract
Abstract. Hydrological studies in small basins are essential for investigating the role of distinct processes on water resources conservation and to assess the impact of the natural ecosystems on improving water security especially in semiarid environments. In Brazil, the cooperative hydrological Network REHISA (“REde de HIdrologia do SemiÁrido”) comprises hydrologists from several universities of Brazil, focusing on field measurements, monitoring and modeling activities in well instrumented experimental rural catchments located at different regions and biomes in Semiarid environment. Water scarcity is a common aspect among the catchments, as well as risks of soil and water degradation. The objective of this work is to present assessments of near surface soil moisture spatial-temporal distribution, and to evaluate the impact of soil conservation techniques in reducing runoff, using small-scale experimental plots in a representative catchment of the Pernambuco State, Brazil. The study catchment is located in Alto Ipanema River Basin (AIRB) (with an area of 150 km2), which is located at the semiarid region of the São Francisco River (area of 641 000 km2). Soil and water monitoring was performed in experimental plots with different soil cover conditions (Bare soil plots; Plots with natural cover – Caatinga Biome vegetation; Plots with cactus Palma barriers; and Plots with mulch cover – Dry grass mulch at 4 t ha−1), where probes were installed for high resolution soil moisture assessment. In addition, regular soil moisture monitoring campaigns were conducted at 7 different locations, using a capacitance probe, with arboreal and shrub Caatinga vegetation, pasture and bare soil, predominantly Brachiaria decumbens. Mulch cover runs close to the Caatinga cover, but still with higher runoff generation, and presenting lower soil moisture temporal mean values. Caatinga was highly effective in terms of soil and water conservation at the small basin scale for both the dry and the wet season, resulting in a positive nexus between vegetation and water availability at the region.
Highlights
Near-surface soil moisture plays an important role on ecohydrological processes, influencing the partitioning of precipitation into infiltration and runoff, and controlling evapotranspiration (Grayson et al, 1997)
In spite of the experimental period of only 2 years, it can be verified from data that Caatinga cover efficiently contributes for the highest soil moistures, for the wet condition due to infiltration, while mulching is effective in maintaining higher soil moisture for dry soil scenarios, for soil moisture values lower than 0.15, approximately the field capacity soil moisture
The study successfully addressed the role of Caatinga natural cover and of conservation practices for soil and water conservation in a semiarid ephemeral basin, where evapotranspiration usually exceeds rainfall
Summary
Near-surface soil moisture plays an important role on ecohydrological processes, influencing the partitioning of precipitation into infiltration and runoff, and controlling evapotranspiration (Grayson et al, 1997). A better understanding of the spatio-temporal distribution of soil moisture is crucial for several applications, including soil conservation, environmental protection and rainfed agriculture. Field hydrological studies in small basins allow investigation of the relative role of distinct processes on soil and water resources conservation (McClain, 2013), and the impact assessment of agricultural conservation practices on water security and soil protection, especially in semiarid environments. According to Maneta et al (2008), the discontinuity of the processes in semiarid areas both in space and in time produces a highly complex discontinuous nonlinear rainfall– runoff relationship, interfering on infiltration and lat-. Montenegro et al.: Moisture Dynamics and Runoff under Different Cover Conditions in Semiarid Brazil
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