Simulating impacts of irrigation on the hydrology of the Karagan Lagoon in Sri Lanka PDF Download
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Author: Philipp Stanzel
Publisher: IWMI
ISBN: 9290904852
Category : Irrigation projects
Languages : en
Pages : 63
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Book Description
The extension of the Uda Walawe irrigation scheme in southern Sri Lanka may have a significant ecological impact on the development area and its downstream wetlands. The evaluation of this impact is the subject for a long-term study that is presently being carried out by the International Water Management Institute (IWMI). In this study, the pre- development environmental conditions in the area are being investigated and the changes caused by the new irrigation system will be monitored in the future. Part of this study is a hydrological assessment of the coastal lagoon (Karagan Lewaya) and its small catchment to the south of the evelopment area. The lagoon is likely to receive high quantities of drainage flows from the future scheme. This could deteriorate its water quality and hence affect the suitability of the lagoon as a habitat for migratory birds and might lead to flooding of adjacent settlements.
Author: Philipp Stanzel
Publisher: IWMI
ISBN: 9290904852
Category : Irrigation projects
Languages : en
Pages : 63
Get Book Here
Book Description
The extension of the Uda Walawe irrigation scheme in southern Sri Lanka may have a significant ecological impact on the development area and its downstream wetlands. The evaluation of this impact is the subject for a long-term study that is presently being carried out by the International Water Management Institute (IWMI). In this study, the pre- development environmental conditions in the area are being investigated and the changes caused by the new irrigation system will be monitored in the future. Part of this study is a hydrological assessment of the coastal lagoon (Karagan Lewaya) and its small catchment to the south of the evelopment area. The lagoon is likely to receive high quantities of drainage flows from the future scheme. This could deteriorate its water quality and hence affect the suitability of the lagoon as a habitat for migratory birds and might lead to flooding of adjacent settlements.
Author: Meredith Giordano
Publisher: IWA Publishing
ISBN: 1843391120
Category : Science
Languages : en
Pages : 289
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Book Description
This volume is an analytical summary and a critical synthesis of research at the International Water Management Institute over the past decade under its evolving research paradigm known popularly as 'more crop per drop'. The research synthesized here covers the full range of issues falling in the larger canvas of water-food-health-environment interface. Besides its immediate role in sharing knowledge with the research, donor, and policy communities, this volume also has a larger purpose of promoting a new way of looking at the water issues within the broader development context of food, livelihood, health and environmental challenges. More crop per drop: Revisiting a research paradigm contrasts the acquired wisdom and fresh thinking on some of the most challenging water issues of our times. It describes new tools, approaches, and methodologies and also illustrates them with practical application both from a global perspective and within the local and regional contexts of Asia and Africa. Since this volume brings together all major research works of IWMI, including an almost exhaustive list of citations, in one single set of pages, it is very valuable not only as a reference material for researchers and students but also as a policy tool for decision-makers and development agencies.
Author: Silva, E. I. L.
Publisher: IWMI
ISBN: 9290907789
Category : Nature
Languages : en
Pages : 126
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Book Description
Sri Lanka, an island in the Indian Ocean, has lagoons along 1,338 km of its coastline. They experience low-energy oceanic waves and semidiurnal microtidal currents. The Sri Lankan coastal lagoons are not numerous but they are diverse in size, shape, configuration, ecohydrology, and ecosystem values and services. The heterogeneous nature, in general, and specific complexities, to a certain extent, exhibited by coastal lagoons in Sri Lanka are fundamentally determined by coastal and adjoining hinterland geomorphology, tidal fluxes and fluvial inputs, monsoonal-driven climate and weather, morphoedaphic attributes, and cohesive interactions with human interventions.Most coastal lagoons in Sri Lanka are an outcome of mid-Holocene marine transgression and subsequent barrier formation and spit development enclosing the water body between the land and the sea. This process has varied from one coastal stretch to another due to wave-derived littoral drift, sediment transport by tidal fluxes, fluvial inputs and wave action or, in other words, sea-level history, shore-face dynamics and tidal range as the three major factors that control the origin and maintenance of the sandy barrier, the most important features for the formation and evolution of coastal lagoons with their landward water mass. In certain stretches of Sri Lanka’s coastline, formation of the barrier spit was very active due to shore-face dynamics that resulted in chains of shore parallel, elongated lagoons. They are among the most productive in terms of ecosystem yield and show some similarities to large tropical lagoons with respect to sea entrance, zonation, biodiversity and ecosystem services. However, some of them become seasonally hypersaline due to lack of freshwater input and high evaporation. Functions and processes of some of these water bodies are fairly known. There are a fair number of small back-barrier lagoons of different shapes and sizes whose origin goes back to sea-level history. They are located on low-energy coasts with prominent beach ridges and restricted hinterland geomorphology. Mixing processes of these landward indentations are hindered by elevated sand dunes, and their salinity increases due to poor freshwater input and high evaporation leading to seasonally hypersaline conditions. These sedimented lagoons, primarily confined to the southeastern coast of the island, are biologically the least productive, with limited ecosystem values and services. Another group of moderately elongated semicircular, slightly large lagoons in the same coast, formed exclusively by submergence due to mid-Holocene sea-level rises, do not receive sufficient freshwater input leading to seasonally hypersaline conditions. They are also biologically unproductive but some are ecologically important since they provide habitats conducive to migratory birds. In contrast, some lagoons on the southern coast receive sufficient freshwater via streams draining the wet zone, maintain more estuarine salinities, exhibit rich biodiversity and serve as functional resource units. Lagoons formed by mid-Holocene submergence and recession of water level with simultaneous chain barrier formation on the high energy southwest coast, which includes cliffs, small bays and headlands, show peculiar configurations and link channel characteristics. Some of these irregular water bodies have clusters of small isles and luxuriant mangrove swamps with high biodiversity but not very rich in catadromous finfish and shellfish species due to the restricted nature of the entrance channel and nondistinct salinity gradients. The barrier-built, seasonally hypersaline lagoon complex in the Jaffna Peninsula, the largest lagoon system in the country with multiple perennial entrances show extremely narrow salinity ranges towards the upper limit of salinity. The main lagoon is elongated and the shore parallel to eastward and southward extensions is connected by narrow channels. The other lagoon in the Jaffna Peninsula is elongated, shore parallel and ribbon-shaped and receives tidal water throughout the year but freshwater is received only from precipitation and surface runoff. Even though the lagoons in the peninsula are extremely rich in ecosystem heterogeneity their hydrology and hydrodynamics have been severely disturbed by infrastructural development for transportation and by attempts to create a freshwater river for Jaffna. There are a few virgin lagoons of moderate size also on the northern coast, south of the Jaffna Peninsula on both the east and west sides. They look very typical tropical lagoons rich in biodiversity and biological production but their structure, functions and values are virtually unknown in scientific or socioeconomic terms. The lagoons located on the east coast are not numerous but relatively large in extent. They are also an outcome not only of mid-Holocene sea-level rises but of submerged multi-delta valleys or abandoned paleo estuaries. When inundated, the multi-delta valley configuration became elongated and is shore parallel with a smooth seaward shoreline; both shorelines become irregular when coastal waves are weak, and internal waves are created by the action of local winds. Configuration of a lagoon formed by inundation of an abandoned river valley is irregular with a long entrance channel extended landward. These lagoons are highly productive with a variety of associated ecosystems, large open water areas and wide perennial sea entrances. When the lagoon is too much elongated, zonation is prominent due to fewer entrance effects. Lagoons form a particular type of natural capital which generates use values (fish, shrimp, fuelwood, salt, fodder, ecotourism, anchorage, recreation, etc.) and nonuse values (habitat preservation, biodiversity, ecosystem linkages, etc.) contributing positively towards improving the human well-being. Of many values of lagoons in Sri Lanka, only the extractive values are generally utilized at present, by way of fish and shrimp catches, salt production and use of mangrove for various purposes. Besides, coastal lagoons generate a range of nonextractive use values and nonuse values, which could add towards the total economic value. Misuse has taken place at several instances when “use” adversely affects the status of the resources or the health of the ecosystem due to vulnerability and poverty, population pressure, urbanization, development activities and multi-stakeholder issues. The status of lagoon resources shows that the resources in the majority of Sri Lankan lagoons still remain satisfactory, somewhat good or very good. Nevertheless, concerns for management of lagoons in Sri Lanka exist only where “use values” (extractive values, such as fish and shrimp) exist. There is no evidence of resources management in lagoons for inspirational, scholarly values or tacit knowledge of the same. Management for use values exhibits several stages from zero management to comanagement via community management and state intervention. Most of Sri Lanka’s lagoons have the potential for generating high extractive and nonextractive use values which could improve the human well-being, while maintaining resources sustainability. Unfortunately, these potentials have not been understood or “seen” yet by the relevant authorities, although a few instances of exploring this potential were noticed.
Author: Smakhtin, Vladimir U., Piyankarage, Sujeewa C., Stanzel, P., Boelee, Eline
Publisher: IWMI
ISBN: 9290905387
Category : Coastal ecosystem health
Languages : en
Pages : 36
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Book Description
The impacts of water resources and irrigation development need to be quantified in order to understand the environmental costs of such development activities. Complex data-intensive simulation methods are normally used for this purpose in the developed world. However, lack of reliable data prohibits the use of such models in developing countries where it is more practical to apply models with less data requirements. The report illustrates three applications of simple and pragmatic simulation models to small coastal water bodies in Sri Lanka and South Africa.
Author: Sophie Nguyen-Khoa
Publisher: IWMI
ISBN: 9290905913
Category : Fisheries
Languages : en
Pages : 46
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Book Description
Author:
Publisher:
ISBN:
Category : Agriculture
Languages : en
Pages : 182
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Book Description
Author: Molle, François, Jayakody, Priyantha, Ariyaratne, Ranjith, Somatilake, H. S.
Publisher: IWMI
ISBN: 9290906073
Category : Irrigation
Languages : en
Pages : 48
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Book Description
This report analyzes a case from southern Sri Lanka, where the Samanalawewa dam and the Kaltota Irrigation Scheme (KIS) compete for the water of the Walawe river. At the catchment level, it is shown that dam releases are well attuned to the needs of KIS and to the occurrences of natural runoff, and that little of the dam water is "lost" to the river.
Author: M. Kikuchi
Publisher: IWMI
ISBN: 9290905018
Category : Irrigation
Languages : en
Pages : 64
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Book Description
Increasing the area under irrigation and the widespread adoption of seed-fertilizer technology were the major factors that contributed to enhanced rice production in Sri Lanka, enabling the country to achieve self-sufficiency in rice. In recent years, there has been a shift in emphasis from expanding the irrigated land base to enhancing the productivity of irrigated land through diversification of agriculture and improvement of rice production, with better water management in irrigation schemes. This report attempts to assess how the irrigation sector in Sri Lanka is adapting itself to these new challenges. It analyzes the future direction of irrigation in Sri Lanka in light of recent trends in public and private investment in this sphere, and the revolution in groundwater development brought about by the poor performance and gradual deterioration of existing irrigation schemes.
Author: R. Sakthivadivel
Publisher: IWMI
ISBN: 9290904445
Category : Irrigation
Languages : en
Pages : 38
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Book Description
Coping with scarcity of water supply for managing irrigation under uncertain and inadequate conditions has become part and parcel of many irrigation systems in the semiarid tropics of Asia. Based on a case study of the Kirindi Oya Irrigation and Settlement Project (KOISP) in southern Sri Lanka, this report provides evidence of the uncertain and inadequate inflow into the reservoir and its impact on the seasonal planning.
Author: Smakhtin, Vladimir
Publisher: IWMI
ISBN: 9290906197
Category : Hydrology
Languages : en
Pages : 19
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Book Description
Quantification of hydrological processes and water requirements of aquatic ecosystems is required for many projects related to environmental security and efficient water use in agriculture. This also applies to the Asian monsoon region. This paper focuses on the Walawe River basin, located in a semi-arid zone of southern Sri Lanka. The two major reservoirs in the upstream and middle reaches of the river with a total capacity of 486 million cubic meters (MCM) have significantly affected the hydrology of the river, with associated adverse environmental and social consequences.
