Use of Geographic Information System (GIS) tool in watershed hydrology and irrigation water management
Role of GIS in Micro-Watershed Planning and Management
A GIS is a composite of computer based decision support tools for the integration of spatial data from different sources and for the analysis, manipulation and display of these data. It is therefore, an excellent tool for the management of large bodies of spatially extensive data with all the advantages of a computer environment: precision, consistency and absence of computational error.
This powerful tool holds a very large potential in the field of regional and micro-level spatial planning particularly in micro-watershed planning and management. A GIS can help pull together various types of disparate data such as remote sensing data, census data, records from different administrative bodies, topographical data and field observations to assist researchers, planners, project officers and decision-makers in resource management. Creation of a spatial database is the first step in micro-level planning. This is followed by spatial analysis to help identify problem areas and, finally, the steps towards planning to mitigate problems are taken by marking out action areas. Taking a watershed as the spatial unit of study, appropriate physiographic and morphometric parameters can be taken into account to enable proper micro-watershed management.
Watershed management requires a three-tier management strategy focusing on :
(i) a micro-regional planning approach, (ii) the analysis and appraisal of the biophysical and socio-economic environs and (iii) agro-ecological zoning. The necessity for a micro-regional approach to planning arises primarily because the actual conditions of watersheds vary, depending on the local, biophysical conditions, population pressure and natural resource conditions. ( THAPA, et al. 1992).
Information on existing landuse and landcover, its spatial distribution and changes are essential prerequisites for planning (ANONYMOUS, 1992). Landuse or land-cover changes are critically linked to a combination of natural and human impacts. (TURNER, 1995). An improved understanding of the dynamics of land-use/land-cover changes provide a means for projecting the impacts of landuse. Thus, land-use planning and land management strategies hold the key to development in a region. Geographic Information Systems (GIS) provide an effective tool for analysis of patterns and causes of land-use dynamics and for planning management strategies.
Creating infrastructure to provide support (social) services is a government responsibility and the government has established norms for use in the planning process to cover geographical areas with these services. Whereas, in the plains, the services can reach a greater number of inhabitants; due to (i) a higher density of population and (ii) easy accessibility (few geomorphic impediments); in hilly regions, the placement of these services in tune with the inhabitants' requirements is more difficult. Sometimes even the geomorphic features create seasonal accessibility (such as a river in spate or a snowy ridge acting as seasonal obstacles). GIS applications have the potential for assessing support service requirements and their placements. This application has advantages over the conventional mechanisms, as multi-criteria analysis is not only feasible but much faster with GIS (MENRIS CASE STUDY Series No.5).
GIS as an Integrating Tool
An important feature of applying Information Technology to the handling of spatial data is the ability to link data sets; that is, to merge and compose different data for the same location. Integration, in a GIS context, is the synthesis of spatial and non-spatial information within the framework of an application. This makes a Geographic Information System an analytical and decision making tool fundamentally different from a paper map. By performing operations across the two sets of information in tandem, a far richer set of questions can be answered and a far broader range of problems can be solved than in systems that handle just attribute or spatial data alone.
The ability of GIS to integrate maps and databases, using the geography as the common feature among them has been extremely effective in the context of Planning development. The attribute database can be analysed by multiple queries, linked to multiple databases related to different projects to arrive at a comprehensive picture of the current scenario in a given area. Since the data (for micro-level planning) would be captured from the lowest end of the administrative system (normally at block level - village-wise), the database can be queried for aggregated results at any of the upper administrative levels viz. District, state and national levels.
A GIS, like any Information System normally includes DBMS functions. However, it differs from conventional DBMS in the sense that every data element in a GIS has to be directly or indirectly associated with a map object -- a location on the earth's surface expressed as co-ordinates with respect to some predefined co-ordinate system. Typical data in spatial form could be on general resources like topography, geology, geomorphology, climate; administrative boundaries like state, district, village, forest range; data on infrastructure like road network, power lines, water lines, sewage lines, locational data in the form of latitudes and longitudes; as well as models like ground water flow, soil productivity, timber growth and soil erosion which can be applied to geographic units. The data in non-spatial form could be the descriptive attributes associated with spatial features like soil type, land use type or socio-economic data.
A case study on the development of a Micro-watershed GIS for planners at the grassroots can be cited as an example, in this context.
Case Study
In a project sponsored by the Ministry of Information Technology (Div'n of Applications of Electronics to Rural and Social Development), the Systems Research Institute is creating a special-purpose vector-based desktop GIS for use at the grassroots, which aims at providing tools that are useful to Micro-watershed planners. This software is basically an integration of five different modules :
VIEW: The viewing module enables the user to select/deselect - different features of a map for viewing, contextually-relevant explanatory text or pictures, or to zoom in and out at different scales on a map, to change colours, to select/deselect information to be displayed on-screen when the cursor lies over a map element, to conduct queries, compute length/area and to print out the map.
EDIT: This is basically for a sophisticated user skilled in map-editing. The user will be asked to type in a password to allow him an access to the editing module. This would include map-inputting capability (read-in of a scanned or digitised map); optional input of height information and development of contours, slope and aspect maps; drainage pattern development; volume computation for proposed water storages, land capability classification, creation of proposed landuse maps, etc. The editing capabilities include search - allows one to search for an object on the map, translation of an object in X & Y direction, object creation of different types, object geometry modification, colouring of objects, creation of buffer zones, etc.
DATABASE: This module consists of the software that records, retrieves and manipulates data concerning sociological information, resource information, historical data /normative data and reports/graphical output.
ANALYSIS: This would enable the user to perform different types of analysis -- both spatial and computational, e.g. delineating micro-watersheds from a drainage map, stream ordering, drainage density, calculating maximum basin relief, volume computation for proposed water storages, what-if analysis etc. It also includes hydrological models comprising of different engineering structures for soil and moisture conservation, and water harvesting structures.
HELP: The help module contains the user guide, texts, reference documents and tutorials.
This software is being built using the GeoConcept GIS engine, with Visual Basic. The system will be loaded in a CD (along with texts and reference documents, a user guide and tutorials) and will be distributed by the Ministry of Information Technology in the public domain - i.e. at very low cost. Special efforts are being made to create an extremely friendly user-interface.
The tool is being developed in collaboration with three other organisations - Society for Rural Industrialisation, Ranchi (SRIR); PROGRESS Group, Hyderabad (PROGH) and National Centre for Human Settlements and Environment, Bhopal (NCHSE). The GIS will interface their Foxbase, Access, Excel, etc. files and VB programmes while also providing a general-purpose ODBC database connectivity.
The Alpha-test version of this system is currently ready, and the Beta-test versions are expected before the summer of 2001.