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Erosion in Moroccan Watersheds Can Be Reduced up to 60 Percent Through the Use of Isotopic Techniques


(Photo: Champa Dissanayake/Sri Lanka AEB)

The erosion that plagues Morocco’s hillsides affects more than the agricultural fields that are losing soil. The eroding soil that sweeps down the hillsides eventually ends up as sediment in water reservoirs, leaving them with less water storage capacity. The Joint FAO/IAEA Division, working with Morocco’s nuclear institution and other partners, adapted and introduced a package of isotopic techniques to identify the most erosion-prone areas. Having this information allowed for development and introduction of targeted conservation agriculture solutions. Initial pilot studies indicate that the steps taken have reduced soil loss in Morocco’s Tetouan watershed of the Tangier - Tetouan region and in the Oued Mellah watershed of the Casablanca-Setta region by around 40 and 60 percent, respectively, and, in turn, greatly reduced the sedimentation of the local reservoirs.

Each year, as much as 100 million tonnes of fertile soil is lost from world agricultural systems through soil erosion. In economic terms, the on- and off-farm soil erosion costs for farmers and the world’s land systems are estimated at US $400 billion per year. Moreover, a quarter of the world’s population relies on food produced on degraded lands, which means crops have lower yields and the food produced has lower nutritional value. In Morocco, soil erosion effects up to 40 percent of the total land area. Half of its 20 million hectares of watersheds are affected by high erosion risks, losing around 100 million tonnes of soil each year. Moreover, the eroding soil ends up in reservoirs, which reduces their water storage capacity  by 75 million m3 per year. This means Morocco is losing the ability to store an amount of water capable of irrigating 10,000 ha of arable land each year. In addition, the topsoil that erodes down the hillsides is rich in nutrients, so when it enters the reservoirs, those nutrients feed the growth of algae in the water, which affects water quality and fish populations.

Morocco’s mountainous regions deal with a great deal of soil erosion, due to difficult climatic conditions that combine long drought periods and short intense rainfall, poor soil development due to the steepness of slopes, and a history of unsustainable land management practices, such as overgrazing, deforestation and improper planting schemes. Armed with information about the physical problems, the Joint Division, through the IAEA’s technical cooperation programme, initiated a programme to introduce a package of nuclear techniques that would enable local institutions to identify Tetouan’s areas most prone to erosion. The study combined two isotopic techniques: fallout radionuclides (FRNs) and compound specific stable isotopes (CSSIs), which are further explained in the FRNs-CSSIs box below.

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