From plot to catchment scale: evaluating historical and adapted land management practices in an agricultural watershed in Tajikistan

Societal and agronomic changes during Tajikistan’s post-soviet era have altered the rural farmland management and the related catchment hydrology. The increasing demand for food production and the limited crop diversity eventually affected soil health and surface hydrological processes. Late planting of summer crops, the removal of plant residues and intense soil disturbance through ploughing are accompanied with limited rainfall interception, which fosters runoff and eventually erosion with potentially disastrous consequences in the downstream areas. As part of Caritas Switzerland's Weather, Water, Climate Services (WWCS) initiative, jointly funded with the Swiss Agency for Development and Cooperation, this study assesses the adoption of Sustainable Land Management (SLM) practices at the field level to reduce surface runoff and erosion, while diversifying and enhancing crop production. This study focuses on a 6356 km2 large watershed in the Khatlon region of Tajikistan and couples field experimental runoff plot monitoring with process-based hillslope scale modeling (Water Erosion Prediction Project; WEPP), eventually connected with watershed level hydrological assessment (Soil and Water Assessment Tool; SWAT). Field experimental procedures are being conducted through national, international and local citizen scientists. The study is in its initial phase – however, one season of plot monitoring has been conducted that allows a preliminary assessment of the surface runoff and erosion response of bare, summer wheat, chickpea, alfalfa and esparcet plots. The experiment enables the assessment of the single crops’ performances, as well as integrating crops into rotations through modeling. At the same time, land use and land cover (LULC) ground truthing within the Khatlon watershed was undertaken to validate two freely available global data products provided by the European Space Agency ESA; the CCI LC 300m and the ESA WorldCover 10m datasets. From the ESA CCI LC product, a comprehensive time series from 1992 to 2020 was developed to analyse the changes in LULC within the research area. The validation process enhances the reliability of the LULC data, which is also important for modelling purposes, in the Khatlon region. In a next step, involving multiple stakeholders, land suitability assessment and mapping will yield plausible watershed management scenarios to evaluate the potential of diversification and the introduction of multi-seasonal crops (i.e. alfalfa and esparcet) to reduce surface runoff and sediment yields from the farmlands and to strengthen the local agro-ecosystems and their sustainable production.