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Arunkumar, R.; Jothiprakash, V.
doi: 10.1111/lre.12136pmid: N/A
Irrigated agriculture is the largest consumer of water, with high significance in India as the majority of its people depend on it. Rainfall uncertainties, and uneven distribution of utilizable water over space and time, have presented a serious challenge to irrigation water management and crop production. Surface water reservoirs play a major role in supplying irrigation water and also addressing uneven water distribution to some degree. Varying water requirements for different crops under multiple canals, however, requires that planners develop an optimal crop planning for the efficient operation of a multireservoir irrigation system. The spatial and temporal water transfer within a multireservoir irrigation system necessitates integrated operation of all the involved reservoirs. Thus, integrated operation of a multireservoir system is a fundamental requirement for efficient irrigation water management, and also become a key issue for sustainable agricultural development. This study derived an optimal crop plan for the integrated operation of a complex multireservoir system with intrabasin water transfer, using a multiobjective fuzzy linear programming (MOFLP) approach. The MOFLP model resulted in a level of satisfaction of 0.46, with an irrigation intensity of 102.18%, and a total crop area of 149 232.10 ha. The optimal policies were furthermore assessed with various statistical indicators with a simulation model, indicating they are performing well, with high reliability and resilience for longer periods.
Moses, Sheela A.; Janaki, Letha; Joseph, Sabu; Joseph, Justus; Thomas, Jobin; Lal, Pramod
doi: 10.1111/lre.12137pmid: N/A
Many coastal lakes are under serious threats due to increased pressures associated with population growth, accelerated eutrophication, invasive species and toxic contamination. The extent of the pollution depends almost entirely on the characteristics and processes taking place in the lake basin. The objective of this study was to identify the pollution potential zones (very high, high, medium and low) in the Akkulam–Veli (A–V) Lake Basin (Thiruvananthapuram, Kerala) using GIS‐enabled, multithematic overlay analysis. The primary characteristics considered were geomorphology, lithology, land use, soil, slope and population density. The results of this study indicated the major portion of the lake basin exhibits very high or high pollution potential zones, with the drains passing through the very high pollution potential zone being mainly responsible for the contamination of the lake water. High population density, predominant commercial use and settlement with mixed tree crop, level and gentle slope (low slope) are the factors responsible for the very high pollution potential. The organic pollutants in the lake system increase with the increased extent of the very high pollution potential area. This analysis approach will help authorities to identify the underlying causes of lake water quality degradation and plan and implement effective measures for protecting the lake. This process can also be utilized by scientists elsewhere to facilitate lake protection.
Ghansah, Benjamin; Asare, Yaw M.; Tchao, Eric T.; Forkuo, Eric K.
doi: 10.1111/lre.12138pmid: N/A
Lake Volta is the world's largest man‐made lake by surface area, and the fourth largest by water volume. Located completely within Ghana, it has a surface area of about 8502 km2 (3283 square miles). Like many other lakes on the African continent, Lake Volta is a major natural resource for Ghana, storing water for the operation of the hydroelectric dam, water supply for domestic, agricultural and industrial purposes, habitat for diverse aquatic species, an avenue for recreational activities, means of navigation between the north and south parts of the country, and a climate modulator for the tropical region. The lake has experienced variable water level and surface area changes attributable to climate change and excessive water abstractions. Using histogram thresholding techniques, this study produced binary images and vector maps of the lake. Spatial extent mapping of the lake using Landsat TM 1990, ETM + 2000 and ETM + 2007 images indicated the lake experienced both increased and decreased surface area changes during the study period. The lake's surface area varied by about 197 km2 between 1990 and 2007, with the water level fluctuating between ±7 m. Factors thought to be contributing to these changes include human factors (regulated flows, deforestation, increased water abstractions and pollution) as well as natural phenomenon (climate change, water run‐off and subsequent sediment transport).
Fonseca, André Luiz dos S.; Bianchini, Irineu; Pimenta, Cristiane M.M.; Soares, Cássio B.P.; Mangiavacchi, Norberto
doi: 10.1111/lre.12139pmid: N/A
The formation of reservoirs usually incorporates the inundation of terrestrial vegetation in the basin. The decomposition of organic matter from the flooded vegetation may have several implications for reservoir functioning, including eutrophication and dissolved oxygen depletion. The hydrostatic pressure increases with depth in a reservoir, and its influence on the decomposition process has not previously been evaluated. This study was undertaken to evaluate the decomposition of terrestrial plant detritus of different qualities (leaves and branches) under different hydrostatic pressure conditions. Detritus were placed separately in glass bottles in the laboratory and incubated in tight stainless steel pressure vessels, simulating three different depths (surface, 30 and 100 m). The masses (mg) of particulate organic carbon (POC), dissolved organic carbon (DOC) and inorganic carbon (IC) were determined for the 4 months of the detritus decomposition simulated in this study. The mass values were transformed in percentages of the initial detritus carbon. The results of temporal variations of the compounds studied were fitted to a first‐order biphasic decay model. The hydrostatic pressure exhibited no significant effects on litter decomposition. On the other hand, the detritus chemical composition (i.e. the presence of labile and refractory compounds) was the determining factor for the decomposition curve shape and for the differences observed between the leaves and branches. The greatest POC loss from leaves, and resulting larger DOC mass, indicated the leaves were more labile than the branches. The results also indicated the branches are the main detritus remaining in a reservoir over time.
Elazegui, Dulce D.; Rola, Agnes C.; Allis, Erica
doi: 10.1111/lre.12141pmid: N/A
This study examined the current governance system for Lake Buhi, Philippines. It describes stakeholder patterns of decision‐making, their roles in the decision‐making process based on their legal mandates, the manner of interactions, the sources of conflict and how these various issues are currently resolved. Stakeholders represent diverse interests, including irrigation, hydropower generation, fishery management and navigation. This study uses data generated from ten key informant interviews of the different stakeholders, information from five round table discussions, and secondary data and reports of various agencies. The results indicate that Lake Buhi and its watershed present classic man‐in‐nature governance challenges. The interplay of internal and external uncertainties regarding multiple uses results in a complex system that is difficult to effectively manage. Climate‐related hazards aggravate the pressures from activities within the lake watershed, complicating water allocation issues. The institutional arrangements that have emerged to address these challenges, however, appear to be fraught with overlaps, fragmentation and a lack of communication. It is thought these deficiencies could be addressed by establishing a lake basin council with representation from all the involved organizations, as well as any stakeholder groups not represented by organizations. The system of governance over the lake must address issues concerning water uses and access to the resource. The capacity of the organizations to participate in such an arrangement is weak, however, and capacity building is needed. The availability and sharing of data and information among stakeholders are also weak and must be strengthened if the work of the lake basin council is to be based on the best available information.
Mohammad, Mohammad E.; Al‐Ansari, Nadhir; Issa, Issa E.; Knutsson, Sven
doi: 10.1111/lre.12142pmid: N/A
Mosul Dam, located on the Tigris River north of Iraq, is experiencing sedimentation problems, especially near the Al‐Jazeera pumping station that supplies the irrigation water for the Al‐Jazeera project. The sources of the sediment accumulated within the reservoir are from the Tigris River, as well as ten side valleys on both sides of the reservoir. The sediment inflow rate into the reservoir and the released values are considered on the basis of the operation schedule of the dam for the considered period from 1986 to 2011. The sediment loads were estimated on the basis of available measurements and estimated literature values. The HEC‐RAS 4.1 model was used for flows and sediments in the main river and reservoir. The model was calibrated for flow simulations (coefficient of determination r2 = 0.87) and sediment routing based on bed level, (with resultant r2 = 0.98 and Mean Absolute Deviation of 0.95). The Ackers–White equation was used in the HEC‐RAS model for sediment routing because of the wide range of sediment sizes in the study case. The resultant total accumulated sediment load volume was 1.13 km3, a value that is very close to the measured values (1.143 km3) obtained from a previous bathymetric survey. Furthermore, the model indicated most of the sediment (80.7%) was deposited during the first five of the dam operation.
Dutta, Subhasri; Sen, Dhrubajyoti
doi: 10.1111/lre.12144pmid: N/A
Construction of dams causes reduced flow velocities, inducing gradual deposition of sediments carried by the inflowing stream, and resulting in sedimentation and ultimately diminishing reservoir storage capacity. This study focuses on sedimentation of Hirakud Reservoir in Odisha, India, using available reservoir capacity and numerical simulation data. Reduced trap efficiency, observed and projected capacity curves, rising reservoir bed level and the capacities of the different storage zones for various projected years are analysed. The area‐reduction method indicates the loss in the live, gross and dead storage will be 58%, 63% and 100%, respectively, of their original capacities by 2057, which represents 100 years of impounding of water in the reservoir. If the present sediment inflow rate continues without regular flushing of the deposited sediment, it is predicted the reservoir bed level will rise to the full reservoir level of 192.02 m by the year 2110. Brune's trap efficiency and step method indicate the gross storage zone of Hirakud Reservoir will be completely depleted by the end of 2110, with the trap efficiency reduced to zero. The empirical area‐reduction method is found to be more suitable for determining the storage capacities of Hirakud Reservoir in the absence of sedimentation survey data. An attempt was also made to solve the combined hydrodynamic and sediment transport equations numerically to predict morphological changes in Hirakud Reservoir. The finite‐element code TELEMAC‐2D and finite‐volume code for SISYPHE, respectively, were applied to solve the above set of equations in order to predict the bed profiles at different reservoir cross sections for the period of 1958–2008. Analysis of the simulated results demonstrates that, considering the model inputs, the model performs well in simulating the morphology and dynamic characteristics of a reservoir. Projection of the numerical results indicates a complete loss of reservoir operational life due to sedimentation by around 2150.
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