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

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 20 m 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 stations was 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:

1. Hills and pediments with rocky outcrops with poor soil formation and can support only sparse vegetation.
2. Steep slopes causing high erosion.
3. The existing sparse vegetation of thorny scrubs provides very little protection against erosion.
4. Growing cattle population (local and migratory) and rampant grazing has led to depletion in vegetative cover.
5. Illegal felling of trees to meet fuel wood demands.
6. Lack of awareness among the local people.
7. 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.

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

Acknowledgements
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.