Assessment of the Impact of Contour Ridge Benches on the Soil Water Content in the Watershed of Wadi Siliana (Medjerda Basin, Northern Tunisia)

Soil water content (SWC) is one of the main parameters determining crop yield in semiarid regions. SWC is characterized by high variability, both in space and time, and is strongly impacted by climate change. Soil and water conservation techniques (SWCT), such as contour ridge bench (CRB), are often used to reduce erosion and to increase available water for crops in arid and semiarid areas. In this study, the Siliana watershed in Northern Tunisia was selected as an investigation area for assessing the impact of CRB on SWC. The impact of CRB on SWC was evaluated at the end of the agricultural season 2017 and 2018. To assess SWC, data were collected from image satellite, using Google Earth Engine platform (GEE) and observed precipitation. The thermal optical trapezoidal model (TOTRAM) was applied to draw the relationship between land surface temperature (LST) and normalized difference vegetation index (NDVI) to estimate SWC. The current study carried out at 22 sites. They were selected, one half with CRB and one other without CRB. Results indicate that the estimated SWC in areas with CRB was higher than those without CRB, suggesting the beneficial effect of CRB over SWC. The additional SWC varies among sites between 1 and 6%, during March to early May and drops to be in range < 1% during late May and June, corresponding to the end of the cropping season.