A Gis-Based Parametric Analysis of Irrigational Tanks in the Oldest Civilized City in India-Madurai

The irrigational tanks being traditional Water harvesting structures designed by rulers and chieftains dating back centuries. These are constructed in such a way that they act as a major water resource in drought-prone rural communities. The main aim of this paper is to develop a GIS-based Parametric Maps of Maximum Capacity(MC), Maximum Water Level(MWL), Ayacut Area(AA), Water Spread Area(WSA), Sub-basins and Basins of irrigational Tanks which form the basic irrigation information system to assist agriculturalists, farmers, and Government organization for the proper maintenance of irrigation tanks with suitable indexing parameters, to mitigate & forecast the water and food requirements by evaluating currently available water for the given population density and irrigation lands. The study area selected is the oldest civilized city in India which is in the state of Tamilnadu-Madurai district, which is served by the Vaigai River and consists of 1338 tanks. This GIS-based information system assists the decision-makers to perform surveillance, evaluate the efficiency of the tank at any space & time and take proper managerial methods to utilize the resources economically.


Introduction
Agriculture, being the lower backbone of our country's economy, relies absolutely on water resources. Water plays a major role in all living lives. It is known to be the Elixir of Life. Water resources are available as rainfall, ponds, lakes, rivers, and groundwaters. Water covers 71% of Earth's surface which accounts for nearly 326 million cubic miles of area. 97% is filled as the ocean which is nearly 320 million cubic miles of area. The remaining 3% is the usable freshwater. 2.5% is locked up as glaciers and ice caps, atmosphere, and soil. 0.5% of water is found utilizable which is continually accumulated, filtered, and circulated back again. Due to the rise in the Earth's temperature, IOP Publishing doi: 10.1088/1755-1315/1032/1/012010 2 drastic changes in rainfall patterns affect irrigation. Hence there is a vital need for proper maintenance and storage of irrigation tanks and rainwater. Also, water is taken into consideration to be the factor that's essential for improvement planning.
India receives total precipitation of about 4000 x 10 9 m 3 . Out of this, water available on the surface accounts for 1780 x 10 9 m 3 . But only half of the available surface water can be used due to other restraints. 420 x 10 9 m 3 of water is available as groundwater. Due to the erratic rainfall pattern, water availability is extremely unbalanced. Precipitation is limited to as it were almost 3 to 4 months with 20-45 critical blustery days within the year. Consequently, there is a crucial need for the proper storage, management, and required use of rainwater in places like Lakes, Tanks, Ponds, Aquifers, Reservoirs for conventional and communal resolves.
The irrigation tanks act as a natural and customary way of rainwater harvesting especially in places that are scarce of water. Tanks are low earthen bund that is built along with the tilt of terrain as well as valleys to store the precipitated water. Tamilnadu contains almost 39,202 tanks which are scattered all over the state. The system of a tank consists of a command area, sluice outlets, field distributaries, surplus weir, channel feeder, water spread area, catchment area, and tank bund. Over the years giant damage to the capable applicability of several tanks had been an acting reason of overwhelming siltation, immoderate infection, and encroachments. GIS plays an important part in enhancing the information system which is adapted in the rural areas to make decisions and sustain management functions of that particular area [10]. Thus, GIS will be an advancement in the field of agriculture in locating tanks, identifying their water level and other parameters for the prolonged functioning of agricultural activities.
Irrigation tanks are used recurrently for agriculture, humans, and cattle as drinking water. The possible outcomes from tank irrigation were assessed and concluded that this system may be a productive technology in financial, natural, and societal terms, but under current circumstances of administration, the conditions of these tanks are worsening [4]. Proper communication and knowledge of all these irrigation tanks would help society in many ways. Thus, the information system assists the management of resources. [17].
The proper management of runoff water leads to rainfall -surface water inside a catchment could be a beneficial resource of water to supply high demands [5]. The administration can receive societal endurance of tank rehabilitation projects if they could tackle the multifaceted issues and concede that irrigation tanks benefit the common people in addition to farmers [16]. The surveillance of irrigating crops & inaccessible areas like contours of reservoir water is made easier by Remote sensing techniques which involve reduced manpower, are cost-effective, precise [9]. The approach for economically unifying aerial photography and satellite data with surveys of ground to obtain current guideline information with respect to resources of tanks and irrigated areas under their command [23]. The strategy for the classification of water bodies based on various parameters is essential and effective [22].
Taking into consideration other productive uses (except domestic and cattle), the total production increases 13%, and the cumulative income received by tanks increases by 213% [14]. The research suggests that the correlation could be related between the potential storage and the diffusion area of the tanks. With the usage of remotely sensed images, Water spread areas can be mapped exactly [15]. The production of sustainable crops needs better performance than small training structures tanks, that require reconstruction of physical structure, effective distribution of water in agricultural fields, as well as in farmers, and correct maintenance of the reservoir system after modernization by the participation of farmers [1]. Urbanization was considered the main cause of the drastic runoff of catchment (40 to 60% of rainfall). For this reason, the availability of seasonal water in each reservoir in watershed waters was observed incoherent (0 to 15%), with the summer which comprises about the minimum water memory (0 to 8%) [21]. Geospatial technologies such as remote sensing and geographic information system (GIS) serve as effective aids to assess these impacts of sustainable development in a water management system [19]. The contribution of this paper includes developing a GIS-based tank information system for the study area, creation of parametric Maps of tanks with the satellite image as a base Map and the analysis of parametric maps to understand the present status of irrigation tanks in the study area for future planning and development.

Study area
The study area chosen is Madurai district in Tamil Nadu, India. Madurai District is in the Southcentral Region of Tamilnadu lying between longitudes E 77° 2' and E 78° 2' and between latitudes N 9° 30' and N 10° 27'. Madurai has been an important settlement for two millennia and is one of the oldest continuously inhabited cities in the world. The general slope of Madurai District is from West to East. The geographical area of the district is 3741.73 square kilometres, has a cultivating area of 150704 ha & consists of 7 Basins. All the required non-spatial and spatial data on the command area for all tanks in Madurai district (1338 tanks) were collected.

Database
In this paper, all required non-spatial and spatial data on the command area for all tanks in Madurai district (1338 tanks) were collected (

Methodology
The digital database of non-spatial and spatial data about the command area has been created in the GIS environment. As prime work for this project, the satellite data of the Madurai region were downloaded from the BHUVAN portal.
Furthermore, (1/4) th details of data have been verified for data accuracy through field visits. All data combined with the acquisition of new data related to technical aspects of Tanks were verified with the Latitude and Longitude coordinates of Tank location using a GPS device. The spatial database was created using QGIS (Quantum Geographic Information System).

Digitization of Boundaries
The Map of the Madurai district and its taluks have been downloaded from the Madurai district corporation website. Using BHUVAN data as a base map, this district and taluk map have been georeferenced using QGIS. Then we have digitized the boundaries of Madurai district and its seven taluks in QGIS using the above-georeferenced data (Fig. 3).

Parameters Taken
The following are the parameters taken related to Irrigational Tanks which come under the Irrigation Engineering of the Civil Engineering domain.

Maximum Capacity (MC) of Tank
Gross volume of water which can be stored in the Tank/storage structures.

Maximum Water Level (MWL) of Tank
The Water level is reached during the passage of the design flood. It depends upon the specified preliminary reservoir level and the spillway gate operation rule. It is also called the Highest Flood Level (HFL) or Highest Reservoir Level (HRL).

Ayacut Area (AA) of Tank
The area that is served by the Tanks for irrigation purposes is the Ayacut Area of the tank.

Water Spread Area (WSA) of Tank
It is an area covered by water, i.e., land of the Tank occupied by water (submerged area).

Sub-basin of Tank
Sub-basin is a structural geological feature in which a larger basin is divided into a series of smaller basins with intermediate intra-basin heights.

Results and Discussion
From the analysis of various geospatial data as well as non-geospatial data, the numerical decisions have been estimated using simple Mathematics which have been given below,

Application & Use of GIS Map
With the inference from each parametric GIS Map of Madurai tanks as well as generic irrigation IOP Publishing doi:10.1088/1755-1315/1032/1/012010 7 tanks all over the world, we can conclude that applying Information System will help to reduce the Encroachments and siltation in the water spread areas of Tanks, supply channels, and surplus courses, which take precautions to mitigate Major flood loss. Using this data, the Government can allocate relief funds for farmers who have lost their grown crops in their field due to natural calamities like cyclones, floods, heavy rains, etc. These data directly contribute to the region of Natural wellness meant for potential & productive agricultural areas and give a clear vision to protect those particular areas with immense beneficiary data. With the cumulative capacities of tanks, currently, available water for the given population density and irrigation lands can be evaluated.
Proper rationing of water for both domestic purposes as well as agricultural utilities can be validated. Cost for Maintenance of Conduits and its new installation can be done in a very effective manner. Seasonal opening of sluices may be decided by knowing the Capacity of Tank. It also greatly helps to increase the depth of the Tank and to meet the future forecasted water requirements which would be found by Mathematical modelling. By monitoring the water level by taking these values as extreme values Major flood loss can be mitigated. An alarm for timely Desilting of Tank (Desiltation process) can also be given. Geological /Soil Analysis data combined with our obtained data can be combinedly used to suggest suitable agricultural crops that can be cultivated in those regions concerning uniform Sub-Basins.
With the help of this data, Renovation/Repair work in any particular Sub-Basin can be made since repair work simultaneously affects the series of Tanks associated with the particular Sub-Basin. These data enable us to directly measure the available surface water in the particular zone, which can be an index factor for balancing the eco-systems. Using these data, the Government can easily allocate funds for State Public Works Department (SPWD) and Central Public Works Department (CPWD) for the Civil repair Project.

Conclusion
Tank irrigation is an economical technology and proper management of tanks for agriculture and irrigation is the need of the hour. By providing an effective tank information system, current obstacles in agriculture and water resource management can be resolved. A study was conducted at Madurai district, Tamil Nadu, with the objective of developing a GISbased irrigation tanks information system to assist the agriculturalists and governmental administrators for proper planning and management. Thus, irrigational tanks information was collected for various tank attributes including Maximum Capacity (MC), Maximum Water Level (MWL), Water Spread Area (WSA), Ayacut Area (AA), Sub-Basins, and Basins were uploaded in GIS to process the data. The study revealed that spatial, as well as non-spatial data, can be integrated and analyzed in different formats. Results in the form of maps, tables, and graphs were acquired with the help of GIS which could help farmers, irrigation engineers, and government officials to maintain the tanks' performance and resources effectively.