Water Balance and Soil Moisture Deficit of Different Vegetation Units under Semiarid Conditions in the Andes of Southern Ecuador

Andreas Fries,Fernando Oñate-Valdivieso,Karen Silva,Pablo Ochoa-Cueva,Franz Pucha-Cofrep

doi:10.3390/cli8020030

Andreas Fries, Fernando Oñate-Valdivieso + Show 3 more

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https://doi.org/10.3390/cli8020030

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Abstract

Water availability in semiarid regions is endangered, which is not only due to changing climate conditions, but also to anthropogenic land use changes. The present study analyzed the annual and monthly water balance (WBc) and the soil moisture deficit (Ds) for different vegetation units under semiarid conditions in the Andes of southern Ecuador, based on limited meteorological station data and field measurements (soil samples). To calculate crop evapotranspiration (ETc) the Blaney–Criddle method was applied, and the specific crop factor (Kc) included, because only temperature (T) and precipitation (P) data were available. By means of the soil samples the water retention capacity (RC) of the different soil types present in the study area were estimated, which, in combination with WBc, provided reliable results respective to water surpluses or deficits for the different vegetation units. The results indicated highest Ds for cultivated areas, particularly for corn and sugarcane plantations, where annual deficits up to −1377.5 mm ha−1 and monthly deficits up to −181.1 mm ha−1 were calculated. Natural vegetation cover (scrubland, forest and paramo), especially at higher elevations, did not show any deficit throughout the year (annual surpluses up to 1279.6 mm ha−1; monthly surpluses up to 280.1 mm ha−1). Hence, it could be concluded that the prevailing climate conditions in semiarid regions cannot provide the necessary water for agricultural practices, for which reason irrigation is required. The necessary water can be supplied by areas coved by natural vegetation, but these areas are endangered due to population growth and the associated land use changes.

Highlights

Water and fertile soils are fundamental for agricultural development [1]
The limited water availability in semiarid regions, together with the predicted changes in climate conditions, combined with unsustainable water management and land use changes, complicates agricultural development, which is confirmed by the observed decrease in food production (e.g., [18,19])
Orthent and Hemist soils had a sandy loam texture, Udalf and Tropept a loamy clay texture, Tropept and Orthent a clay texture, and Torret a loamy sandy clay texture. By utilizing this information bulk density (BD), CC, permanent wilting point (PWP) and retention capacity (RC) could be calculated for each specific soil type (Table 2)

Summary

Introduction

Water and fertile soils are fundamental for agricultural development [1]. these resources suffer natural degradation due to erosion processes, floods and droughts as well as from anthropogenic impacts such as deforestation and other land use changes [2,3]. As the Fifth Assessment Report of the Intergovernmental Panel on Climate Change indicates [7,8], quantity and quality of water will change in many parts of the world, especially in semiarid regions where the water supply is sensitive to precipitation amounts and evaporation rates, which restrict local water availability Soils in these regions generally have low natural productivity and low fertility due to the pronounced precipitation cycle [9], which, in combination with the frequent occurrence of droughts, complicates agricultural development [10,11]. In semiarid regions, the economic development of the local population depends principally on agriculture, and on local water availability [12,13], for which reason the observed altered climate conditions and population growth, as well as unsustainable water management practices endanger the availability of this hydrological resource [14]. The limited water availability in semiarid regions, together with the predicted changes in climate conditions, combined with unsustainable water management and land use changes (population growth), complicates agricultural development, which is confirmed by the observed decrease in food production (e.g., [18,19])

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