Home Articles Catchment Characterization of Loktak Lake using Remote Sensing And GIS

Catchment Characterization of Loktak Lake using Remote Sensing And GIS

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:

  • Creation of temporal spatial database using satellite data for catchments (1995, 2000 and 2004-05) and structural components/ habitat types of wetlands
  • Generation of Land Capability map for the catchment area for long term and short term management plan such as formulation of soil conservation plan to check soil erosion and subsequent silting up of Loktak Lake.
  • Collection, integration and modeling for suggesting sustainable management solution for conservation of Loktak Wetland.

4. DATA USED/SOURCES.

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.

Table 4.1 Data Source

Sl. No Satellite Data Path Row Date
1 IRS-1D LISS-III 14 50 Dec. 2003, Jan,2006, Feb.2001
2 IRS-1C LISS-II 14 50 March 1994
3 IRS-1D LISS-III 15 51 April 2000, Jan.2002
4 IRS-1C LISS-II 15 51 March1994
5 LANDSAT –TM 14 50 1994
6 SPOT MLA 14 50 1989,1999
7 PAN 14 50 2003,Dec.
8 IKONOS     Oct. 2002, Dec 2003

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 :

  • Land use/cover
  • Hydrogeomorphology
  • Slope
  • Drainage
  • Road network
  • Settlements.

A.Land Use/Cover :
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.

Table 5.1 Land use- catchment area 2004

Sl.No. Land Use classes AREA (IN HA)
1. Built up land 15448
2. Agriculture land 37055
3. Dense forest 586
4. Open forest 10160
5. Degraded forest 3514
6. Scrub forest 6042
7. Shifting cultivation- abondoned 1093
8. Shifting cultivation- current 718
9. Aquaponds/ waterbodies 2331
10. Marshy / swampy land 509
11. Hill / hillocks 705
12. Wetland 25839
13. Total 104000

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).

Table 5.2. Structural components of wetland area 2004

Sl.No. Habitat type/ zone Area (in Ha)
1. Open Water 2634
2. Dense Phum 9176
3. Moderate Phum 1058
4. Sparse phum 1744
5. Aquaponds 6911
6. Agriculture 32
7. Island with vegetation 288
8. Island without vegetation 66
9. Settlement 80
10. Phum Ring area 3841
  TOTAL 25830

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.

Table 6.1 Land Use : Loktak Catchment Area

Sl. No. Land use Classes Area (in Ha)Years
1990 1995 2002
1. Built up land 14558 14608 15359
2. Agriculture land 37735 36572 36453
3. Dense forest 1493 1153 4541
4. Degraded forest 9312 10716 9585
5. Scrub forest 9732 9777 7330
6. Shifting cultivation 3131 2369 2127
7. Marshy / swampy land 631 419 84
8. Grassland/Grazing Land 391 304 141
9. Hill / hillocks 755 755 755
10. Aquaponds/ waterbodies 974 1988 2471
11. Wetlands 25312 25339 25154
  TOTAL 104000 104000 104000

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

Table 6.2 Land Capability Classes : Loktak Catchment

Sl.No. Land Capability Class Area (Ha.)
1. IIIe2s2 1800.06
2. IIIe2s3 1063.61
3. IIIe2w1 3062.82
4. IIIw3 10446.89
5. IIe1w1 10928.59
6. IIw2 8637.92
7. IVe2s2 937.40
8. IVe2s3 1572.45
9. IVe3s3 3586.77
10. IVw4 5333.07
11. VIIe3s3 3850.49
12. VIIe4s2 811.79
13. VIIe4s3 3077.94
14. VIe3s2 3518.89
15. VIIe3s3 3631.12
16. VIe4s3 1234.08
17. Vw4 5046.54
18. Waterbody 20142.11
19. Settlements 15315.82
  Total 103998.36

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.

Table 6.3 Recommendation and suggested land use in different capability units

Land Capability Grouping (units) & Locations   Major Soil Constraints Recommendations/ Suggested Land Use
1   2 3
VIIe4s3 Mostly in high hills covering Ireng, Nungjang, Troglobilok, Churachandpur, & Liklai
    Very steep slopes
    Stoniness
    Very severe erosion hazard Very strong to extreme soil acidity Low exchange capacity and base status
    Shifting cultivation and land slides
    Rill and gully erosion control by putting small check dams at frequent intervals; plantation of forest species in open areas with proper soil conservation of existing forest .
    VIIe4s2 In high hills covering Sinda Bagan Leriong, Tairen Pokpi . Churachandpur Khoupum
      Steep to very steep slopes
      Very severe erosion hazard
      Very strong to extreme soil acidity
      Low exchange capacity
      Low base status Jhum cultivation
      Gully erosion control with check dams, restriction of felling, firing, grazing, etc., plantation of forest species with proper soil conservation measures.
      VIIe3s3 Mostly in hilly terrain covering Kangchup R.F., Kangchup Chiru RF. Bherum, Khonga Khul, Mairangching Khunou, Churachandpur
      Moderately steep to very steep slopes
      Severe erosion hazard Stoniness
      Very strong soil acidity
      Low CEC and base status Shifting cultivation
      Contour terracing to protect the terraces; restriction of free grazing, firing, forest cutting; plantation of forest species are suited in this region.
      Vie4s3 Mostly in hilly terrain covering Kangchup, Natokon, Lamdan, Kholrok and Parengba.
        Moderately steep to steep slopes
        Stoniness
        Very severe erosion
        Very strong soil acidity
        Low exchange capacity
        Shifting cultivation and land slides
        Preservation of existing forest from firing, tree cutting, jhuming, grazing etc. and plantation of suitable forest species; provision for diversion channel and vegetative waterways. Contour terracing by putting stones to protect the terraces and gully erosion control.
        Vie3s3 In hilly terrain covering , Sungang, Ireng, Bherum, Tairen Pokpi, Mairangching Khunou, Laipham, Gothol,
          Moderately steep to steep slopes
          Stoniness
          Severe erosion
          Very strong soil acidity
          Low CEC and base status
          Jhum cultivation
          Afforestation of open areas, protect from jhuming, and grazing. Provision for diversion channel vegetative waterways and contour terracing.
          Vie3s2 Mostly in hilly terrain covering Kangchup Chiru, Kangchup Makhon, Natop, Tairn Pokpi, Ngariyan
            Moderately steep slopes
            Severe erosion
            Very strong soil acidity
            Low base status
            Shifting cultivation
            Provision of diversion channel and vegetation waterways. Terracing by putting the stones to protect the terraces; preservation for existing forest from tree cutting, firing, grazing etc. along with agro silvi pastoral programme.
            Vw4 In very low lying areas covering Charaibung, Khonumla and Karang.
              Very severe limitation of water stagnation/ flooding
              High water table
              Very poor drainage
              May be used for pisciculture and cultivation of waterchestnut with proper agronomic practices.
              IVe3s3 Mostly in foot hills and isolated hillocks covering Kangchup, Meirang Ching Khunou, Mashemjang,
                Moderately steep to very steep slopes
                Stoniness
                Very strong soil acidity
                Low CEC and base status
                Jhum cultivation
                Maintenance of existing terraces by cover crops and plantation of perennial grass of legume variety; selected areas may be brought under fruit trees and other orchard crops with proper soil conservation and agronomic practices.
                IVe2s3 In foot hills covering Bijan Tampok, Lonphal, Laching Manbi and Mairangching Khunou.
                  Moderately to moderately steep slopes
                  Stoniness
                  Very strong soil acidity
                  Moderate erosion hazard.
                  Low CEC and base status Shifting cultivation
                  Plantation of economical species on the ridges of the terraces, horticultural crops/ orchard crops in the side slopes with proper conservation measurers.
                  IVe2s2 Mostly in foot hills covering Bijang Tampok, Woynan, Isham Khuman and Mairangching Khunou
                    Moderately to moderately steep slopes
                    Moderate erosion hazard.
                    Very strong soil acidity
                    Low base status and exchange capacity.
                    Proper maintenance of existing terraces, provision for vegetative waterways, cultivation of plantation crops along with agro forestry.
                    IVw4 In low lying plains covering Thinnuggai, Ishok and Naurem
                      Very severe water stagnation Very poor drainage Cultivation of suitable varieties of paddy along with pisciculture; improvement of drainage.
                      IIIe2s3 Mostly in foot hills covering Khonga Khul, Chingphel, Kelthenmanbi, Rharyeng
                        Moderate slopes
                        Moderate erosion
                        Stoniness
                        Strong soil acidity
                        Low CEC
                        Proper soil conservation measures may help in growing various horticultural and plantation crops.
                        IIIe2s2 In lower slopes of foot hills covering Rharyeng Khunoi, Parengba, Bungte Chiru,
                          Moderately slopes
                          Moderate erosion
                          Strong soil acidity
                          Low CEC and base status
                          A variety of horticultural and plantation crops can be grown with proper soil and water conservation practices.
                          IIIe2w1 Mostly in gently sloping plains covering Khongathel, Koirentak Khunou,
                            Moderate erosion
                            Slight stagnation of water Imperfect drainage.
                            These lands are suitable for rice and selective crops can be grown during winter season.
                            IIIw3 Mostly in nearly level to very sloping plains covering Khabi, Kamong, Awangjiri, Oksong-bung, Kwasiphai
                              Severe limitation of water stagnation
                              Poor drainage
                              These lands require drainage improvement and some selective crops can be grown during winter season.
                              IIe1w1 Mostly in very gently sloping plains covering Phaiyeng, Tairen Pokpi,
                                Slight stagnation of water Imperfect drainage These lands are suitable for rice and a number of crops can be grown during winter season.
                                IIw2 Mostly in very gently sloping to nearly level plains covering Khongarthel,
                                  Moderate stagnation of water Imperfect drainage. These lands are suitable for cultivation of kharif rice and a number of crops can be grown during winter season.

                                  Fig 6.1 Pictures of Loktak and its Catchment with DEM modeling.

                                  REFERENCES:

                                  1. Anon (1994) ” Wetland Mapping Projet- Implementation Plan” Space Application Centre, Ahmedabad.
                                  2. Brivio P.A., Giardino C. and Zilioli E. (2001). Validation of satellite data for quality assurance in lake monitoring applications. The Science of the Total Environment, 268 (2001) 3-18
                                  3. C.L.Trisal and Th.Manihar (2002). “Management of Phumdis in Loktak Lake”. Proc. Management of Phumdis in Loktak Lake, Imphal, Manipur.
                                  4. National Bureau of Soil Survey & Land Use Planning (2002) “Land Capability of Loktak Catchment Area of Loktak Lake” Nagpur, Maharastra, Report No. 594.
                                  5. Roy, De Rashmi(1993) “Wetlands of India”. Shish Pubhishing House, New Delhi.
                                  6. Singh N.S., Singh N.R., J.K.Garg, T.V.R. Murthy (1997) “Wetland of Manipur” MARSAC and Space Application Centre, Hyderabad 26-27pp.