Case study on artificial recharge using Remote Sensing and GIS

Dr. M. Ramalingam
Scientist, Institute of Remote Sensing, Anna University, Chennai – 25
[email protected]

Dr. A.R. Santhakumar
Director, Institute of Remote Sensing, Anna University, Chennai – 25

Abstract
With the increasing use of groundwater for various activities the fast decline in groundwater takes place. In order to prevent the aquifer from fast depletion, the artificial recharge is resorted to. Keeping this in mind to avoid fast decline in groundwater levels in various parts of Tamil Nadu, a study has been undertaken to identify the favourable areas for artificial recharge and suggest suitable recharge structures to augment the aquifer system. The analysis was carried out blockwise for the entire state of Tamil Nadu using Remote Sensing data and GIS techniques. The various thematic maps such as Geomorphology, Geology, Soil, Slope, Landuse, Drainage, Drainage density, Lineament density, Runoff isolines, Depth to weathered zone, Depth to Basement, Groundwater level fluctuations and water quality were used in the analysis. The above maps were prepared using IRS-1C LISS III satellite data and other collateral information collected from the field and digitized. Criterion tables were generated considering the importance of different themes and necessary ranks and weights were assigned to each theme. Using ARC/INFO GIS software, the above themes have been integrated and the areas suitable for artificial recharge have been identified. Considering the 1-sigma criteria, the favourable areas for artificial recharge has been categorized into highly favourable, moderately favourable, less favourable and poor for recharge and verified in the field. Considering the terrain conditions and favourable zonation, the suitable artificial recharge structures such as percolation pond, check dam, recharge pit, recharge shaft, contour trench, nallah bund, recharge tube wells and subsurface dyke were recommended. These recommendations were communicated to district administration for implementation.

Introduction
With the increasing use of groundwater for Agricultural. Municipal and Industrial needs, the annual extraction of groundwater are far in excess of net average recharge from natural resources. Consequently, groundwater is being withdrawn from storage and water levels are declining resulting in crop failures, seawater intrusion in coastal aquifers, land subsidence etc., Vagaries of monsoon and indiscriminate development of groundwater often result in declining trend of groundwater levels. There is an urgent need for artificial recharge of groundwater by augmenting the natural infiltration of precipitation into subsurface formation by some suitable method of recharge. Artificial recharge is one method of modifying the hydrological cycle and thereby providing groundwater in excess of that available by process. Keeping this in mind to avoid fast decline in groundwater levels in various parts of Tamil Nadu, a study has been undertaken to identify the favourable areas for artificial recharge and suggest suitable recharge structures to augment the aquifer system. The analysis was carried out blockwise for the entire state of Tamil Nadu using Remote Sensing data and GIS techniques.

Objectives
The following are the objectives of the study:

• to delineate areas favourable for recharge by integrating various themes with different recharge possibilities and
• to recommend suitable recharge structures.

Procedure Adopted
This study was carried out for the entire state of Tamil Nadu to improve the overall groundwater level so as to prevent the wells extracting groundwater to a larger extent. Special thrust is given for the wells extracting water for drinking water. The description of the study area and the various procedures adopted in this study is briefly explained below:

Description of the Study Area
The Tamil Nadu has a geographical area of 1,30,000 sq.km. Majority of the area of Tamil Nadu was covered by the two major domains of geological formations namely hardrock and sedimentary. More than 70% of the area of this state falls under hard rock domain. The sedimentary formations occurs all along the coastal zones consists of coastal sandy zones, river alluvial sandy formations. The average annual rainfall is around 1000mm. In this project, it was contemplated to harness the excess surface water and allowed to recharge the aquifer.

Description of the Study Area
The Tamil Nadu has a geographical area of 1,30,000 sq.km. Majority of the area of Tamil Nadu was covered by the two major domains of geological formations namely hardrock and sedimentary. More than 70% of the area of this state falls under hard rock domain. The sedimentary formations occurs all along the coastal zones consists of coastal sandy zones, river alluvial sandy formations. The average annual rainfall is around 1000mm. In this project, it was contemplated to harness the excess surface water and allowed to recharge the aquifer.

Data Used for Integration
In this Project both satellite data as well as extensive field data were used for preparation of various thematic maps . As far as satellite data is concerned IRS-1C LISS III data has been procured for the entire state and used in the analysis. In addition to LISS III data IRS-1C PAN data also consulted for better interpretations. In addition to the above satellite data, the following collateral data namely daily rainfall, groundwater levels, geophysical data, borehole data and water quality were used in the analysis.

Spatial data used for Integration
In this analysis, 12 layers of thematic information are used. Among the 12, the following seven basic maps namely (a) Geomorphology (b) Geology (c) Soil and Hydrological soil (d) Slope (e) Landuse (f) Drainage and (g) Transport network and settlement are used. The above maps were prepared using both the satellite data and toposheets. In addition to the above basic layers, the following derived layers such as drainage density, lineament density, maximum groundwater level variations, depth to weathered portion and water quality were used. These maps were generated using ARC/INFO and SURFER softwares.

Processing of Data
The thematic information generated through visual analysis were digitized using ARC/INFO GIS ——– recharge. The first rank classes are considered as most favorable zone for recharge and the fourth rank is for poor recharge. These ranks were assigned to each theme. Apart from the ranks, weights among the parameters were assigned based on group discussions and expert opinion. The different criterion tables are developed for hard rock, sedimentary and alluvial formations. The criterion table developed for hard rock formation is shown in the Table – 1.

Spatial Analysis of Data
Using the overlay module of ARC/INFO workstation based GIS software, the above thematic layers were overlaid with suitable ranks and weights. The final map contains numerous polygons having the characteristics of all the above 12 themes. In order to group them in to four classes, a statistical analysis was made assuming the distribution is normal. Considering the 1 – sigma criteria using the above criteria, the final suitability map has been delineated into four classes namely highly favorable, moderately favorable, less favorable and not favorable.

Field Verification
The generated output maps were taken for field verification. The scientist verified the zonation created using GIS and also the suggested type and location of the water harvesting structures. In almost all the cases, the zonation generated as well as the type and location of water harvesting structures suggested are agreeable and the success rate is more than 90% while suggesting the suitable recharge structures, the zonation map, drainage pattern, site conditions etc., have been considered.

Recommended Recharge Structures
After detailed analysis of the zonation map generated using GIS techniques, the various suitable recharge structures such as check dams, percolation ponds, recharge pits / shaft, subsurface dykes, nallah bund, contour trench etc., were suggested based on the field condition.

The brief description of the different structures recommended are given below:

Percolation Pond in Dindigul
In Dindigul area the quality of water was bad due to infiltration of tannery effluent in the nearby places. Since the water was not completely affected and it is brackish in nature, if the groundwater is recharged through percolation pond, there is every chance in the improvement of the groundwater. Keeping this in mind, the percolation pond has been suggested near Dindigul in Dindigul block (vide Fig – 1a). Moreover, the structures has been suggested in the highly favourable zone to ensue more recharge. Similar types of percolation ponds were suggested wherever the highly favourable zone with suitable terrain conditions are exist.

Check dams in Chinnamanur block
The Odappatti village in the Chinnamanur block is suffering from water scarcity. The wells sunk in the area got dry and they did not give sufficient yield. In order to improve the groundwater potential three check dams have been proposed (vide Fig-1b). The location where the check dam proposed falls under highly favourable zone with good potential of groundwater.

Subsurface dyke in Bhavani River
The subsurface dyke is a semi permanent structure constructed across the river where sand thickness is more. The subsurface dyke will be constructed above the bed level of river and upto the sand thickness. This is normally recommended near the sea shore to prevent the subsurface flow from the river to the sea. But this subsurface dyke is proposed to prevent the movement of sand in the river. (vide Fig – 1c).

Recharge Pit in Kovilpatti
The recharge pit is normally recommended where the soil is having poor infiltration rate. If the clay layer is present above the shallow aquifer, the clay will be removed by constructing small pits. These pits will be filled with pebble stone and sand. Whenver rain occurs, the water seeps through the recharge pits and recharge the aquifer. The Kovilpatti area having full of black cotton soil lacks the recharge capability. In order to improve the above aquifer, the recharge pit (vide Fig-1d) has been recommended. If the depth of clay formation is more instead of recharge pit, recharge shaft has been recommended.

Similarly the other recharge structures such as nalla bund, contour trench etc., were suggested wherever feasible. Desilting of tanks were also suggested in some blocks.

Conclusions
At the present condition, the artificial recharge is to be resorted to sustainable development of groundwater. Hence, the results obtained from the present study fulfill some of the requirements of selecting suitable artificial recharge structures. Moreover, this is one of the first operational study made for identifying suitable sites for artificial recharge structures using Remote Sensing and GIS. The criterion table developed in this study should be slightly modified according to the site conditions.

Acknowledgement

• The authors thank Dr. K. Kasthurirangan, Chairman, ISRO / Secretary., DOS and Mr. Nambiyar, the then Chief Secretary to Government of Tamil Nadu for taking initiative for commissioning the project.
• The authors are indebted to the Secretaries to Government, Department of Municipal Administration and Water Supply and Department of Rural Development, Government of Tamil Nadu for sponsoring the project and the encouragement. The authors wish to express their deep appreciation to the Vice-Chancellor, Anna University for the encouragement given during the execution of the project.
• The authors acknowledge the services rendered by the consultants and the members of the Technical Committee and Quality Evaluation Team for successful completion of the project.

References

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• Bansky Vladimir (1983) Artificial Recharge study in Madras Aquifer – The Hindu (Daily) June 1983.
• CGWB, Govt. of India (1992) Proceedings of workshop on “Artificial Recharge of Groundwater Lowcost Rain Water Management for increasing irrigation & Groundwater Recharges in Chattisgarh Region” Held at Raipur, India.
• Chow. V. T. (Ed. 1964) Hand book of applied Hydrology MoGrow Hill Book Company, New York.
• Edward, T. Ooksford (1985) Artificial Recharge : Methods Hydraulics and Monitoring, Artificial Recharge of Groundwater, Edited by Takashi Asano.
• Ramalingam. M. & Natarajan. T(2000) Identification of recharge areas using Remote Sensing and GIS” NNRMS Bulletin (B) 24. Bangalore, India.