Micro-Watersheds Information System

Micro-Watersheds Information System

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Dr. S. Mohamed Ghouse, A. Kalyani, Y. Farid sali Khan
Agriculture Engineering Department
Chennai-600035, Tamil Nadu.   Watershed is a hydrological unit bounded by natural ridges and allows the run-off due to rainfall to drain in a well-defined drainage pattern of streams flowing within the watershed’s boundary. As an integral part of area development programme, land resources development programmes are taken up on micro watershed basis as the shape of the watershed controls the natural resources like water, soil and productivity of the land for successful implementation of agriculture, forest and other eco-restoration programmes. The watersheds are delineated in the District Atlas in 1:50000 scale and further delineated as smaller units like sub watershed, mini watershed and micro watershed Grade 1 to micro watershed Grade 5.

The micro watershed is generally consisting of second order streams. For the micro level development in each ha of a watershed the micro watershed and the village becomes the most adaptable unit. However for regional planning and management, the watersheds and districts are the most workable units. For demonstrating the effect of GIS managing the resources even at block level, the Tenkasi block maps on various themes like Village, Land use from satellite data, drainage, geomorphology, geology etc are taken. It is clear that GIS will become an indispensable day-to-day management tool to manage natural and human resources efficiently at state level as well as for the smaller units like blocks in this millennium.

Use of watersheds in regional planning at micro and macro levels
The Western Ghats Development Programme (WGDP) area and their district boundaries are used to create a GIS of WGDP area in Tamil Nadu. The spatial information of forest area from satellite data, meteorological data such as rainfall and non-spatial data such as number of labourers are added. This spatial and non-spatial data in the attribute tables makes one to understand the present condition of the area. Based on the thematic maps generated using the ArcView GIS software it is possible to study the present Western Ghat Development Plan area in Tamil Nadu and their district boundaries are used to create a GIS status and one can plan for future by generating various maps based on the available infrastructure, human and financial resources. Both spatial and non-spatial data for the Western Ghats Region in Tamil Nadu are taken for the concept of application of GIS for Regional Planning and management. The spatial and non-spatial data for Tenkasi Panchayat Union have been taken up to explain the use of the large-scale information on land use, geomorphic, micro watershed, drainage information in managing the watershed development programme at block level.

GIS in WGDP
The WGDP programme is being implemented in Tamil Nadu in the Western Ghats Region covering parts of Coimbatore, Dindigul, Erode, Theni, Madurai, Virudunagar, Tirunelveli and Kanyakumari districts. With the district boundaries the GIS of WGDP area is created so that the same map can be used to create various thematic maps. The area under WGD Programme is detailed in the Table 1.

Various thematic maps can be generated adding non-spatial data in each column e.g. for management of the scheme, the project cost each year for the districts can be added. The area covered under programmes like soil conservation, afforestation, horticultural plantations, added in the table and map for each theme can be generated. A study might be conducted to assess the effect on each physical target and achievement, thematic map may be used for each budget allotment. Adding query shells we are able to know the changes for permutation of allotment. In fact, infinite number of columns can be added and number of thematic maps can be prepared. The effect in changes due to physical and financial changes can be studied and programme can be monitored at regional level at District as well as at State Programme managers’ level.

For management of a land-based programme at block level more detailed information on land use, village Drainage, Geology, Soils, and Micro-watersheds, etc. are needed. The thematic maps are generated using Topographic sheets in 1:50000 scales. The Taluk maps, Satellite data, Aerial Photographs are used to map various themes. Here the maps for Tenkasi Panchayat Union in Chittar watershed in Tirunelveli District are created using Arc View software. Themes are Drainage, Sub watersheds, Land use as per IRS-1A satellite data, Revenue Villages, Geomorphology and Geology. The GIS has been created in Arc View Software. The attributes tables are simultaneously created. Adding various fields like Area, Priority etc. we can make the GIS effective with non-spatial data as well as spatial data. The Attribute tables of six layers are created simultaneously. With this map, we can create query shells to know the information about the watershed. Complex mathematical equations can also be used to study soil erosion or hydrological characteristics of the watershed.

Table 1: WGDP Project Area in each District

ID

District

Area in ha

1

Nilgiris

HADP

2

Coimbatore

597439

3

Erode

221906

4

Dindigul

374494

5

Theni

293611

6

Madurai

110637

7

Virudhunagar

231749

8

Tirunelveli

600431

9

Kanyakumari

167184

Micro watershed GIS
GIS, created with various layers such as the drainage, village boundary, geology, geomorphology, micro-watersheds etc. will be the foundation and a basic tool for management and planning in watershed development programme. The watershed code number, the revenue village and area of the watershed number are the essential information for any developmental activity which are available in this information system. Since this work is carried out by GIS software, it is possible to add any data to the attribute table of the micro watersheds or the attribute table of the village and make it a good management tool.

If the area covered and cost of work in that year can be added to the attribute table for the Micro watersheds in a Panchayat Union, the maps will be generated by the GIS software for the amount spent and area covered. If query shells are created we can interact with the micro watershed GIS system and know the required information and also study the area based on various non-spatial data added to the attribute table. If the layer such as land uses from land records and satellite data, geology, rainfall, runoff, geomorphology, stream morphology are added, it will become a complete information system on land resources in the Panchayat Union.

The road ahead
Application of complicated formulae in evaluating run-off, soil erosion estimation studies can be done for using the computing facility available in the attribute table. The latest spatial data on land use from satellite data and non-spatial data on demographic features and infrastructure facilities on health, education, transport etc. can be added to this GIS to study the demographic, infrastructural conditions at present and future can be estimated.

The GIS on Region, Panchayat Union or watersheds can reduce the dependence on using the probability or regression models and equation in studying the behaviour of that area during monsoon rains. Using the computing capability of the GIS software these work can be completed in a shorter time effectively and economically. The real time monitoring of an area in rainy days or drought conditions is now a possible and it is easy job for the field staff using the Regional/Panchayat/Watershed Geographic Information system. Thus GIS is going to be the effective management tool to the nation to plan, execute and evaluate the land-based programme in this new millennium.