Hydrology and Erosion Risk Parameters for Grasslands in Central Asia

Central Asia contains a wide diversity of rangeland biomes, including shrub dominated and grass dominated ecosystems. In this chapter, we demonstrate hydrology and erosion dynamics and risks using the USDA-Rangeland Hydrology and Erosion Model (RHEM). Plant foliar and ground cover are important elements in protecting the soil surface from raindrop splash, accelerated runoff, and subsequent erosion. A field site near Yntaly, in the Karagandy Province, Kazakhstan [vegetation classification 38, Kazakh steppe (Stipa capillata, Festuca valesiaca, Artemisia frigida, and A. schrenkiana)], consisting of three different vegetative states representative of varying plant composition and plant cover dynamics was used to parameterize RHEM. In addition, slope effects on hydrology and erosion was also evaluated. The three vegetative states are represented in a state and transition model, consisting of a historic reference plant community, and two additional states depicting moderate and heavy disturbance. RHEM model estimates show increases in runoff and erosion, especially as slope increases, plant cover decreases, and plant composition on the site changes from native plants to more invasive weedy species. The RHEM model is designed to evaluate hydrology and erosion risk with varying land management scenarios. In the United States, the RHEM model is used in rangeland National Resource Inventories, where data on plant species cover and production are collected to assess hydrologic function. On-site resource inventories are needed throughout Central Asia, as different accounts of rangeland conditions have been published. Discrepancies of reported resource conditions on the Kazakh steppe may be due to data and interpretations made from remotely sensed imagery without sufficient on-site ground correlations. There is a desire and need to expand livestock enterprises throughout Central Asia; however, before monetary investments proceed, it is imperative to have reliable information about plant status, production, invasive plants, existing wind and water erosion, and socioeconomic trends. A robust three-tier methodology for rangeland resource assessment is recommended and should include: (1) a field protocol to collect vital on-site rangeland resource data; (2) drone surveillance correlated with field sample – to expand the extent of the field based sample, and (3) remote sensing imagery with the intent to correlate all three assessment protocols. This set of three resource assessment protocols enacted regionally or throughout a country could provide vital needed resource information that would enable realistic determination of levels of rangeland and soil health. This information is critical for determining economic and ecological sustainability of rangelands as different grazing systems are implemented.