Optimizing mechanized micro water harvesting technique can help restore degraded rangelands in Jordan, a research using Rangeland Hydrology and Erosion Model suggests.
Population growth, refugee movement, and boundary restrictions affect the livelihoods of nomadic communities and increase pressures on fragile rangelands throughout the Middle East, including Jordan’s Badia. Overgrazing, caused by an increase in livestock herds degrades native vegetation and harms the soils, which leads to decreased rainwater infiltration and retention capacity, accelerating surface runoff and erosion.
Optimizing traditional techniques
To cope with water scarcity, communities in Jordan have traditionally applied simple yet efficient water harvesting (WH) techniques. ICARDA developed that concept further and mechanized the approach, creating small and intermittent ridges across the sloping land for capturing the excess rainwater. Through intermitting the hill slopes this technique also prevents erosion. Native shrub seedlings, provided by US Forest Service project (SEED), were planted in water harvesting troughs at a research site approximately 10 kilometers (km) from the Jordanian capital, Amman; the troughs acting as ‘vegetation islands’ that would grow and spread out over time.
In order to optimize micro water harvesting and the revegetation of degraded rangeland ecosystems, ICARDA has been promoting a special Vallerani plow, among other techniques, which is composed of a reversible mouldboard and deep ripper. The moulboard creates a micro basin to mainly collect water, but also seeds, topsoil and organic material, while the ripper digs an underground splitted furrow for better water infiltration and storage.
A recent study, jointly carried out with USDA ARS scientists around Dr. Mark Weltz, research leader at the Great Basin Rangelands Research (GBRR) Unit, Nevada, uses the Rangeland Hydrology and Erosion Model (RHEM) to investigate water and sediment dynamics, thereby optimizing the design of the Vallerani water harvesting system. RHEM helps comparing actual stage degraded conditions, mainly due to overgrazing and barley agriculture, with a micro WH restoration scenario.
RHEM is in use to simulate runoff and erosion for the interspacing between the WH structures helping to optimize the implementation design. The model is forced through a 300-year rainfall time series generated by climate generator CLIGEN, thus to investigate long-term hydrological behavior and to conclude on the occurrence probability of certain events. A risk assessment approach will be further developed that considers variable thresholds of surface water yields, both minimum and maximum, as well as erosion and consequential sediment accumulation to better understand the impacts of the micro-WH pits on the ecosystem. This will support the decision making process for targeted Badia restoration efforts – towards a multi-criteria tool trading off shrub growth, water retention, soil conservation and biodiversity.
The research was supported by the USAID-funded Water and Livelihoods Initiative (WLI), the Arab Fund for Economic and Social Development (AFESD),the International Fund for Agricultural Development (IFAD), the OPEC Fund for International Development (OFID) and the US Forest Service. Shrub seedlings were provided by USFS/Hashemite Fund nursery, Sabha, Jordan, through the SEED project for rangeland restoration.
Author: Stefan Strohmeier, Associate Scientist, Soil and Water Conservation (ICARDA).