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Catchments Characterization of Loktak Lake Using Remote Sensing and Geographical Information System (GIS) Techniques Rajkumari Sunita Devi Manipur Remote Sensing Applications Centre Pradeep Srivastava Deptt. of Limnology, Bharkhatullah University, Bhopal Asha Gupta Dept. of Life Sciences Manipur University Abstract The catchment of a wetland has direct bearing on its ecological stability as it is the source of water and matter. Loktak Lake, situated in the Indian State of Manipur, is located between 24°25’ to 24°42’N latitude and 93°46’to 93°55’E. It is a shallow wetland with depth varying from 0.5m to 1.5m. The lake falls under the sub-basin of the Manipur River and its direct catchment occupies an area of 1040 sq. km. The topography of the direct catchment area is an undulating terrain having elevation of 780 metres at the foot hills and about 2068 metres at the highest peak. There are about 98 villages with a total population of 21,334 (1991 census). A number of streams originate from the hill ranges, which lie on the western side of the Loktak Lake, and drain directly into it. Some of the major streams include Nambul, Nambol, Thongjaorok, Awang Kujairok. Awang Kharok, Ningthoukhong, Potsangba, Oinam, Keinau and Irulok contributing significant amount of silt to the lake during the rainy season. Using IRS-IC, IRS-ID, LISS-III&IV data, PAN Data and IKONOS, a detailed study of the catchment area of this important Ramsar Site has been carried out. Different thematic maps like Hydrogeomorphology, Contour, Drainage, Road Network, Settlements and Land Use have been prepared at 1:25,000 scale by using merged data from PAN and IRS-LISS IV image. Information on land use pattern especially the extent and spatial distribution, is a pre-requisite to derive information on temporal change. Land use data, which is generated by this study, helps in identification of areas where immediate attention has to be taken for reviving various landscape elements. It also enables formulation of long term and short term management plans to restore this wetland. Visual and digital analysis techniques were used to prepare the thematic maps. Digital Elevation model of this catchment area is also prepared in order to monitor the water extent which has been affected due to the construction of a dam called Ithai barrage at the southern tip of the lake. Keywords: Manipur, Loktak Lake, Catchments, Thematic Maps, IRD-ID, LISS IV, PAN DATA, DEM 1. INTRODUCTION Manipur, the eastern most state of India between 92 o 59’E to 94o45’E longitude and 23o50’N to 25o41’N latitude, straddling the international border between India and Myanmar, has a peculiar situation in the eastern Himalayas and watershed area of the great river basin systems the Brahmaputra and the Irrawady. It is blessed with an enormously rich heritage of wetlands. Topographically it is surrounded by seven ranges of hills and the valley lies in between. Therefore, wetlands, in Manipur are mostly found in the valley area and are known by the generic name Pat (pronounced as paat).The surrounding hill districts are also replete with many kinds of wetlands, great and small (Wetlands of Manipur, Vol-I- 1999). The pats of Manipur are known to have their own life-span and hydrologic characteristics related to the evolving geo-physical character of land itself. In the beginning of the 20th century there were nearly 500 pats in the Manipur Valley, covering a large position of its area. Loktak lake after acclaiming Ramsar site is well known internationally but apart from Loktak other well-known pats of Manipur are Ikop pat, Pumlen pat, Waithou pat, Ngakra pat and Loushi pat. Loktak lake is the largest freshwater wetland in North-eastern region of India and is situated between 240 25’ to 24042’ N latitudes and 930 46’ to 93055’E longitudes. This lake was designated as wetland of International Importance under Ramsar Convention in 1990 because of its biological richness where naturally occurring phumdis (floating vegetation) covers the lake extensively and is a specialized habitat for many biotas besides being useful to the local people in many ways. The Keibul Lamjao National Park in the southern part of the lake is also a unique floating wildlife reserve and the natural home of the endangered Manipur brow antlered deer, Sangai. Deforestation and shifting cultivation in the catchment has accelerated the process of soil erosion resulting in the lake shrinkage. The nutrients from catchment area and domestic sewage from Imphal city carried by Nambul River are discharged into the lake which is another major problem of the lake (LRIS Report, 2003). All these activities have direct bearing on ecological stability of the lake. 2. STUDY AREA. Loktak has direct catchment of 1040 sq. km and falls under the sub-basin of the Manipur River. The catchment area lies between 24o24’to 24o57’ N latitude to 93o40’ to 93o58’E longitude. The topography is undulating having elevation of 780 m at the foothills adjoining the central valley and about 2068 m at highest peak. There are about 98 villages with a total population of 21,334 (1991 census).  Fig. 2.1 Location Map of Loktak Catchment Area The presence of Ithai Barrage, a multipurpose project for generation of hydel- power and irrigation which was commission in 1983 at Ithai at the southern nearest tip of Loktak, has brought about drastic hydrological changes. Loktak catchment area comprises the elongated hilly terrain of various altitudes along with isolated hillocks, plains and marshy lands. Altitude of elongated hill ranges and isolated hillocks varies between 820 to 2068 meter and 760 to 1100 meter above mean sea level respectively. The rock formations in the catchment area are cretaceous limestone, the Disang with Serpentinites (Lower to Middle Eocene-Upper cretaceous), the Sumas and the Thipams (Miocene). Surma group occurs in the lower reaches of hills where as the Disang and Thipam groups occur in high reaches of hills. Disang formation comprises grey sandstone-grit-conglomerate limestone sequences intruded by serpentinites containing minor amounts of enstalite, chromite, amphiboles and magnetite. The Surma and Thipam groups represented by argillaceous and arneceous sequence respectively. 3. OBJECTIVES The present study lays the foundation for developing wetland conservation models using remote sensing and geo-spatial technologies. Some of the detailed objectives of the study area:
The database of this catchment study consists of primary, secondary and integrated database of spatial and non-spatial data on different components of the catchment. Census data of 1991 & 2001 is used for socio-economic studies of the hill and valley region. Table 1.2 gives the list of satellite data use.
5. METHODOLOGY / THEMATIC MAPS: Visual and digital image interpretation techniques were used to prepared thematic maps on 1:50,000 for 1990, 1995, 2000 using 23.5 meter resolution data of IRS-1C, 1D and 1:25,000 for 2004 -05 using high resolution data like IKONOS , for some area and merge data of 2.5 meter resolution using LISS-III and PAN data . Secondary data for socio-economic etc are also incorporated. The thematic maps are :
Information on Land use/cover pattern, especially the extent and spatial distribution is a pre-requisite to derive information on temporal changes. The land use /cover information helps to identify areas where immediate attention has to be taken for reviving various landscape elements. The present status of land use (Table 5.1) in the catchment is useful for identifying locations for taking up soil conservation measures by involving village communities, for minimizing land degradation.
The land use class of wetland is further classified by preparing a structural components map of Loktak wetland area which shows various classes of phums, agriculture land, islands, aquaponds etc. In the present study SOI topography map of 1970 was use as a base to delineate water spread and demarcate wetland boundary. IKONOS data was use for preparation of the structural component map of 2004-05 (Table 5.2).
 Fig. 5.2 Land use map of Loktak Catchment with wetland area 2004 B.Hydrogeomorphology: Information on landforms is an important input for land management and soil mapping. The aspects of morphology, morphogenesis, morpho chronology and morphometry are vital inputs in preparation of geomorphologic maps. The geomorphic units are delineated based on image characteristics like tone, texture, shape, colour, associations etc. ( Fig.5.2 A). C. Slope: Information on slope is vital for suggesting actions related to restoration plans of landscape. This information is usefull for suggesting checking of soil erosion and drainage related measures. The slope map has been prepared as per IMSD guidelines. Using this information Digital elevation model has been generated using 20 metre contour interval. D. Drainage / Watershed: A drainage map of the study area was prepared using satellite data in conjunction with SOI topography maps. Most of the streams originate from the hill ranges to the west of the lake and discharge water directly into Loktak Lake. Some of the major streams include Nambul, Nambol, Thongjaorok, Awang Kujairok. Awang Kharok, Ningthoukhong, Potsangba, Oinam, Keinau and Irulok contributing significant silt during rainy season to the lake. In all 12 micro-watershed were demarcated and they have been given nomenclature according to the standard of All India Soil and Land Use Surveys (AIS & LUS) of the Ministry of Agriculture. ( Fig. 5.2 B) E. Road Network & Settlements: The road transport network is one of the major criteria for studying and analyzing the socio-economic problem of a certain area and for assessment of impact on the wetland. In the present study, there are three types of roads classified as National highway, Village road and other which may include footpaths etc. The total length of National Highway is 59.652, village road is 723.243 km and others are 234.5 km. (Fig. 5.2.C)   Fig. 5.2 Various Thematic maps of Loktak Catchment Area 6. RESULT AND ANALYSIS i.Spatial Analysis : Land Use Change detection Multi-temporal satellite data have been used for studying land use practices over a period of fifteen years in the catchment of Loktak Lake. It has been found that there is an increase in the built up area and also decrease in scrub forest. There was increase in dense forest from 1990 to 2002. This may be due to some of the activities of afforestation program taken up by LDA for catchment treatment but again this has decline in 2004-05 (Table5.1). There is an increase in open forest area in 2004 and decrease in degraded forest which again shows that deforestation activities have become less and natural regeneration is going on in the catchment area.
There has been an increase in the water spread in the water bodies/ aqua-ponds. This is mainly due to conversion of agriculture and marshy/ swampy land into aquaponds. There is rapid increase in fishing activities in the state of Manipur and annual fish yields from this aquaponds have also increase drastically. ii.Spatial analysis: Land Capability Land capability classification is grouping of soil mainly based on i) inherent soil characteristics ii) external land features and iii) environmental factors that limit the use of land. Classification of soil units into capability groupings enables one to get a picture of i) the hazards of the soil to various factors which cause soil damage, deterioration or lowering in fertility and , ii) its potentiality for production. The grouping of composite units (land use, slope and soil) based upon various individual external factors and inherent soil characteristics suggested by soul survey manual (AIS & SUS, 1970) have been followed. A land capability map showing capability classes ( Fig 1.5 D) and classes given in Table 6.2
As per report on Land Capability of Loktak Catchment Area of Loktak Lake Manipur, published by National Bureau of Soil Survey & Land Use Planning, Nagpur the following table gives some of the recommended and suggested different capability units. The Land capability classes are generated by integrating several thematic maps in GIS.
 Fig 6.1 Pictures of Loktak and its Catchment with DEM modeling. REFERENCES:
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