Effects of Anthropogenic Modification of Karst Soil Texture on the Water Balance of ''Alta Murgia'' (Apulia, Italy)

The "Alta Murgia" region (Apulia, Southern Italy) is a karstic plateau, which constitutes the main recharge area of the Murgia karstic aquifer. The natural morphology of the plateau is defined by widespread surface karst features: karst, karren fields, layers of outcropping rock with discontinuous and thin soils. In general, these soils, relatively thin with sparse vegetation, are primarily used as pastures. Recently, agricultural activities have caused dramatic changes. In particular, ploughing and crushing of the karst surface has led to a conversion of the landscape to fields growing wheat and other crops. Stone clearing practice are carried out by means of the repeated grinding of the carbonate rocks with modern technologies, intensive use of bulldozers and machinery, besides destroying and removing rocks from the fields. Practically, the natural karstic soils were replaced with a layer of homogenous soil, useful for cultivation. This cultivated soil has increased the evapotranspiration and significantly reduced the infiltration thus affecting the water balance and the aquifer recharge. In the present study we analyze the impact of changes in soil texture and crop growth on the water balance in the "Alta Murgia" area by analyzing the features of the newly created soil. The characterization of the modified soil involved both field and laboratory measurements. The HYDRUS 2D model was used to simulate the infiltration process in the unsaturated zone. The objective of this paper is to elucidate the effect of stone removal by presenting a water balance for new soils. The simulations demonstrate that the available infiltration rate at the top layer varies from 60% of the overall amount of rainfall for the bare soil to only 25% in the presence of vegetation. Knowledge of the interactions between vegetation, soil and climate is essential to quantify the vadose zone hydrology and, hence the hydrogeology of the underlying karst system.