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Micro-Watershed development plans using Remote Sensing and GIS for a part of Shetrunji river basin, Bhavnagar district, Gujarat

A. K. Sharma and R. R. Navalgund
Space Applications Centre, Ahmedabad.

A. K. Pandey and K. K. Rao
U. T . D. Barkatullah Vishwavidhyalaya, Bhopal

Micro-watershed level planning requires a host of inter-related information to be generated and studied in relation to each other. Remotely sensed data provides valuable and up-to-date spatial information on natural resources and physical terrain parameters. Geographical Information System (GIS) with its capability of integration and analysis of spatial, aspatial, multi-layered information obtained in a wide variety of formats both from remote sensing and other conventional sources has proved to be an effective tool in planning for micro-watershed development. In this study an approach using remote sensing and GIS has been applied to identify the natural resources problems and to generate locale specific micro-watershed development plans for a part of Shetrunji river basin in Bhavnagar district, Gujarat. Study of multi-date satellite data has reveled that the main landuse /landcover in the area is rainfed agriculture, wasteland with/without scrubs in the plains and undulating land and scrub forests with forest blanks on the hills. Due to paucity of ground water for irrigation, the rainfed agriculture area lacks sufficient soil and moisture to support good agriculture. The agriculture areas along the streams are constantly washed and undergo sheet erosion, thus converting valuable agricultural land into unproductive wastelands. For a major part of the year, the hills remain barren except for few small areas displaying a variety of thorny scrubs and few scattered trees growing along the less assessable slopes. Few varieties of grasses also spring up during the monsoon. The degraded ecosystem has affected the life of the residents within the micro-watersheds. There is always a scarcity of fuel, fodder and water for drinking and domestic use. The depleting vegetation cover has resulted in excessive soil erosion exposing barren rocky wastes. The steep rocky hill slopes facilitate high runoff leading to poor ground water recharge and increased siltation in the village tanks and ponds. According to the local people even today shepherds from adjoining taluka regularly visit to graze hordes of sheep and cattle. In addition to this thereis the problem of the ever-increasing human and livestock population. Thus a heavy pressure exists on the scarce biotic resources of the study area. The main actions suggested for development of land and water resources in the area are being implemented by Mahajanam in consultation with State Government.

Study area details
The study area covering 34 micro-watersheds (28,250 ha.) is a part of Shetrunji river basin in Bhavnagar district, Gujarat and is located between longitude 710 42′ & 710 55′ East and latitude 210 20′ & 210 35′ North. Encompassing Palitana town and 20 other villages with a total population of 69,428 heads (Census, 1991) it receives 454 mm of average annual rainfall. The Shetrunjay hills and the Hastigiri hill are two prominent hills in the study area. The Shetrunjay hills about 603 m above mean sea level (amsl) and Hastigiri hills, 431 m (amsl) with ancient temples are places of religious and tourist interests.

Data Used
indian Remote Sensing Satellite (IRS) LISS-III data at 1:50,000 and 1:25,000 scale of December 1996, January and April 1997 and October, 1988 and collateral data such as Topographical maps at 1: 50,000,Geological / Hydrogeological,Water level and quality maps climate, rainfall data and Census data, etc. have been used

The methodology comprises an integrated approach using multi-date satellite datafor preparation and study of multi-thematic maps at 1:50,000 scale namely Hydrogeomorphology, landuse/landcover (1:25,000 scale), soil, slope, ground water level and quality, etc. Based on subject domain decision rules for land and water management,the integration of the natural resources and demographic theme has been carried out in GIS to identify the problem areas and to providing prescriptions for solving them. The action plan maps thus generated were consequently validated in the field in consultation with local experts. Action plan maps for selected 18 microwatersheds (13940.29 ha.) have been generated at 1:25,000 scale using PAN+LISS III merged data where implementation of plans is to be carried out by Mahajanam.

Observations Theme map details
The details of different theme maps prepared are as below The hydrogeomorphological map comprised seven landform types namely flood plain (7.69 % area), denudational hills (15.10 % area) and residual hills (0.45 % area) over basalt, pediments (2.07 %), buried pediments (64.97 %) and valleys (5.55 %) dissected plateau (4.16 %) and lineaments. The ground water prospects within different landforms vary from good in the plains and valleys to poor and poor to nil in the denudational hills and residual hills.

Landuse /land cover classification using kharif, rabi and summer season satellite data reveled the spatial extent of built up land (3.42 %), forest land (16.88 %), agriculture land (66.85 %), waste land (12.15 %) and others like waterbodies/ stream (0.70 %) etc. The forestland comprised scrub forest (4.08%) and forest blanks (12.80 %). Further classification of forest blanks as forest blanks with good grass (4.37 %), moderate grass (4.84 %) and poor grass (3.60 %) was possible.

Surface water body, drainage and watershed map showing all 34 micro-watersheds and average slope map with seven slope categories have been prepared using SOI topographical maps with 20m contour interval.

The soil map obtained from National Bureau of Soil Survey and Landuse Planning (ICAR), Nagpur showed soils of hilly terrain, soils of pediments and soils of piedmont plains belonging to six series.

Analysis of 17 year (1980 to 1996) monthly rainfall data for five stationswas carried out. The area receives 454 mm average annual rainfall with 25 rainy days.

Factors responsible for degeneration of the ecosystem
Following are based on study of data and detailed field visits:

i) Hills and pediments with rocky outcrops with poor soil formation and can support only sparse vegetation.

ii) Steep slopes causing high erosion.

iii) Theexisting sparsevegetation of thorny scrubs provides very little protection against erosion.

iv) Growing cattle population (local and migratory) and rampant grazing has led to depletion in vegetative cover.

v) Illegal felling of trees to meet fuel wood demands.

vi) Lack of awareness among the local people.

vii) Little concern on the part of the monitoring agencies.

Suggestions and recommendations

Water Resources Development
The main recommendations for water resources comprise a) prospective sites for rain water harvesting / ground water recharge through construction of small, low cost structures using local material and techniques across lower order streams. Structures suggested comprise small masonry check dams (21), nala bund (61) and nala plugs (at regular interval). b) Desilting / deepening / modification of existing tank/pond structures to increase the water holding capacity and facilitate recharge to ground water.

Land Resources Development
The land resources plans depict conservation measures with suitable change in land use/ land cover. Priorities (high, moderate and low) for development has been provided based on existing physical parameters within the micro-watersheds. The suggestions are as given below

  1. Staggered Pits & afforestation with non grazing variety of trees (2733.53 ha.) with high (569.72 ha.), moderate (1116.49 ha) and low (1047.32 ha.) Priority.
  2. Contour trenching & afforestation with non grazing variety of trees (799.22 ha. In Govt. land) with high (432.73 ha.), moderate (196.64 ha.) and low (169.85 ha.) priority.
  3. Contour trenching & silvipasture with non grazing variety of trees (1660.95 ha. Panchayat land) to meet fuel fodder needs.
  4. Pits & afforestation with non-grazing variety of shade trees (about 122.81 ha.) along path to hill shrines.
  5. Protective bunding & Silvipasture (2047.94 ha.) in sheet erosion areas.
  6. Gap filling with protection of forest (1117.13 ha.)
  7. Agro-Horticulture & Field Bund (26.01 ha.)
  8. Double Cropping With Ground Water Exploitation (4416.01 ha.)
  9. Minimum Action (Soil Moisture Conservation) (13752.62 ha.)
  10. Agro-Forestry (117.46 ha.).
  11. No Action (294.39 ha.), and others like river bed, water body etc.

Other significant measures like in general protection of forestland for natural regeneration of vegetation and development of pastureland based on traditional methods in the existing ‘ Gauchar’ land have also been suggested.

Micro-watershed development planning can be done by following an integrated approach using remote sensing data and criteria based analysis in GIS.

We are extremely thankful to Dr. George Joseph, the then Director Space Applications Centre (SAC) for his encouragement and support in carrying out this study. Thanks are also due to Dr. A.K.S. Gopalan, Director SAC for his valuable suggestions.