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UNESCO-IHE Institute for Water Education, Delft (2018)

Impacts of land use change on sedimentation of Mangla Reservoir, Pakistan

Hussain, Imtiaz

Titre : Impacts of land use change on sedimentation of Mangla Reservoir, Pakistan

Auteur : Hussain, Imtiaz

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2018

Reservoirs establish a vital part in human societies. In recent times, they play an important role in managing water resources for sustainable development, growth and poverty reduction of a country. Long term operation of a reservoir is affected by sedimentation. It has adverse effects upon storage capacity of a reservoir, thereby having consequences over the life span of dams. Land use change alters erosion patterns that in-turn changes sediment yield of a catchment. Experimental erosion plots and catchment studies in different parts of the world revealed the sensitive relation between land use, erosion rate and relevant human activities (D. Walling 1999), (Yan 2013). Changes in sediment yield of a basin changes the sediment inflow to the reservoirs. Therefore, all factors that contribute to land use changes in a basin can be considered to have some effect on sedimentation of a reservoir. Many land use types reduce sediment inflow and on the other hand, it is triggered by many other types of land use. Increase in one particular type of land use reduces the other. In this context, the problem seems quite simple at local scale. However, when it is related to other factors affecting sediment yield at basin scale (like surface run-off, soil temperature, slope stability...etc.), it begins to complicate the whole process of sediment yield. For example, urbanization of a piece of agricultural land reduces sediment in-flow at the local level. But it increases surface run-off thereby causing more erosion in some other part of the basin. Therefore, the combined effect of land use changes over sedimentation is rather more complex at basin scale. Since land use change is also associated with sustainable development of human civilization, there is a dire need to study the overall and combined impact of land use changes over sedimentation of a reservoir at basin scale. After Tarbela, Mangla is Pakistan’s second largest reservoir. It was constructed and put into operation in 1967 over the River Jhelum, primarily for irrigation purposes. It also serves the secondary purpose of hydropower generation having total installed capacity of 1050 Megawatts (MW). At the time of commencement, its storage capacity was 7.25 Bm3 that has reduced to 5.76 Bm3 (20.55 % reduction) by 2005. Primary cause of this storage capacity reduction is sedimentation. The impacts of land use changes over sedimentation rates of the reservoir has never been studied using numeric models. This study intends to fill the gap. Identified conditions in terms of land use and weather are considered to simulate sedimentation rate of the reservoir through SWAT modelling (base case). Simulation on the basis of predicted land use is considered to evaluate the future sediment input to the reservoir (reference case).

Sujets  : sedimentation land use reservoirs Pakistan


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