Department of Environmental Biotechnology,
School of Environmental Sciences
Bharathidasan University, Tiruchirppalli – 24, India.
Institute of Remote Sensing,
Anna University, Chennai – 25, India
Availability of water and firewood is shrinking in many regions by 2020. Thoothukudi taluk is the study area. Different thematic layers are prepared using remote sensing and GIS for the assessment of water resources status. The union coverages of land use / land cover, water quality, geology, geomorphology, soil and slope status maps have been incorporated in the Arc GIS environment as input coverages. The existing water resource classes have been reclassified according to the criterion statement, five classes of water resources can be regrouped into three classes such as good, moderate and poor status of water resources in the study area. Overall results show that nearly 50% of the geographical area has good and moderate resources. Another major part of poor resource areas need to be reclaimed to restore and improve its resource status. Resource management planning strategy has been suggested.
The resource management of a nation is controlled by a key factor, that is, its population. India is one of the highly populated countries of the world with the total geographical area is 3.3 million sq.km. The world's population is expected to grow to 7,200 million in the next 30 years (Jacques-Paul Eckebil, 2000). Availability of land, water and firewood is shrinking in many regions. By 2020, Southeast Asia will have less than a hectare of arable land per person. Within just five years, 300 million people, mainly in North Africa, will face critical water scarcities. More than 130 million Africans already live in the areas where firewood consumption outpaces the regenerative capacity of their forests. Deforestation has been put at 18-20 million hectares per annum. The rate of soil loss from agricultural land is in the range of 4.5 to 45.0 kg m-2y-1 of course, it varies with the landscape. Several reports indicate that 3.2 % of the world land area is characterised by bio-diversity loss and tropical deforestation. In India, unfortunately resources such as the wetlands, rivers and tanks have been converted for the improvisation of the agriculture, industry and housing. In most urban centers and the surrounding areas, land degradation and groundwater quality problems are high today (The Environment Survey 2006).
Tamil Nadu is the southern most state on the east coast of India, with a coastal line of about 1000 kilometer. The state comprises of thirty districts. Thoothukudi district is one among them and is located in the southern part of Tamil Nadu. The district administrative headquarters is located at Thoothukudi (Figure.1). The district comprises of seven taluks, including Thoothukudi taluk. The study area of Thoothukudi taluk occupies Middle Eastern sector of the district, stretching over an area of 327 sq.km. It consists of 25 panchayat villages and one town. Thoothukudi taluk is covered by 8?40'N to 8?51'N latitudes and 77?56'E to 78?12'E longitudes. It is bounded by Ottapidaram taluk in the north, Srivaikundam taluk in the west and south and the Gulf of Mannar (Bay of Bengal) in the east with the population of 2, 16,058(Census of India Report 2001). The climate is hot and dry and mostly semi-arid in nature. Rainfall is always scanty and non-perennial streams are prevalent. The maximum temperature recorded so far during the period was 40.5?C in June 1998, and minimum 18.3?C in February 1996. The annual mean rainfall of the study area is 895 mm
Methods and Materials
The base map and slope map of Thoothukudi Taluk has been prepared using Survey of India toposheets 58 L/1&5, 58 L/2, 58 H/13, and 58 H/14 on a scale of 1:50,000. Base map provides the basic information such as road networks, drainage, and tanks taken as control points while transferring the thematic details. Slope map is essential for the resource status analysis of the study area. The drainage lines were extracted from toposheets and watershed map prepared with the use of watershed Atlas of India.
Theme maps have been prepared based on the visual interpretation of the satellite images. Base map has been fixed with imageries on the control points such as the tanks, rivers, drainage and road networks. The features have been identified based on the field knowledge, background information of the study area and using image characteristics such as the tone/colour, texture, pattern, shape, size, location, shadow and association. Features have been identified and mapped based on general guidelines and interpretation key suggested by the National Remote Sensing Agency (NRSA), Government of India, 1994. Geocoded temporal data of IRS 1 C LISS-III (2003) have been used to derive resource maps such as geomorphology, geology and land use land cover and it has been updated with imageries.
Ground Truth Verification
Interpretation and mapping accuracy has been assessed by ground truth verification. For estimation of the accuracy, 30 random points have been selected on the maps to verify on the ground to cover various land use / land cover features, physiography, environmental conditions and degradation types. Error matrix was prepared to minimize the accuracy level. A final correlation has been established by incorporating the corrections found in the field and a final map of the area has thus been prepared.
For the generation of land use / land cover map, thematic maps such as geology, geomorphology, soil and slope have been derived from remotely sensed data and have been given as input to the GIS process to study the water resource status. The overlay analysis of the above coverages has led to the delineation of the water resource units. The Table Criterion Analysis has been carried out in the GIS environment. Attribute data of the, rainfall and runoff groundwater level have also been used during the analysis process. Ranking have been given based on the significance of the parameters of the thematic layers, Rank 1 to 5 imply the status of water resources of the area as excellent, good, moderate, poor and very poor.
Identification of the Resource Status
The various classes of the status such as excellent, good, moderate, poor and very poor have been derived from integrating the results of land and water resources maps. The criterion statement has been prepared for the integration purpose, for resource status maps in the GIS environment.
Thoothukudi taluk is characterised by a flat terrain and there is a vast coastal belt with a gentle topographic gradient towards west. Because of the gentle gradient, there is a possibility of groundwater movement towards east and the landward encroachment of salt water may be encouraged depending upon the situation. The presence of hard and compact sedimentary rocks is the reason for minimal infiltration and the maximum drainage pattern in the taluk area (Appasamy 1994).
The geological formations met within the taluk are alluvial formations covering an area of 20.25 sq.km. Coastal alluvium (marine formation) quaternary found in the eastern part of the study area covers an area of 72.67 sq.km. Fluvio-marine sediments occurs in the upper part and surrounding areas of Korampallam tank, it covers an area south western part of the taluk in the area of 45.44 sq.km. The rock types include hornblende biotite gneiss and quartzite that are found in the hard rock terrain occur in major parts of the taluk and covers an area of 137.65 sq.km in the southwest, northwest and middle parts of the taluk (Figure 2).
The geomorphologic units encountered in the taluk are mostly the pediment complex covering an area of 79% of the total geographical area. The pediment complex includes buried pediment deep, medium, shallow and pediment inselbergs. A sediment outcrop of a eolian plain (teri sand) covers an area of 7.72 sq.km which accounts for 2.35% of the taluk area uplands which are eroded with gullies and pediment groups. Marine plains covers an area of 47.1 sq.km (14.64% of the taluk area) and consists of coastal plain (11.25 sq.km), salt flat (33.62 sq.km), mud flat (1.35 sq.km) and spit (1.72 sq.km) of the total taluk area. Based on the hydrology and soil thickness characteristics the geomorphic features of the study area have been analysed for the assessment of land and water resources status
The taluk has an almost flat terrain with a slope between 0-1%. The general slope of the area is from northeast to southeast. The western part of the study area has a slope of 1-3%. Two elevated small hilly terrains occur in Mudivithandal area where the slope is above 3%
Fig.2 Geology Map
Fig.3 Geomorphology Map
Fig.4 Soil Map
Fig. 5 Watershed Map
The coastal sand and river sand soils are sub grouped as – Puot, covering an area of 43.26 sq.km. Remaining soils have been grouped into four major hydrologic soil groups based on their hydrologic characteristics. The hydrologic soil groups are A, B, C and D. Hydrologic soil group `D' has very slow infiltration capacity and high runoff covering an area of 111.85 sq.km of the taluk. The soils categorised as group `C' has slow infiltration rate and moderate runoff covers an area of 23.32 sq.km. The group `B' with moderate infiltration rate and moderate runoff covering an area of 30.53 sq.km. Group `A' has high rate of infiltration and low runoff, covering an area of 104.68 sq.km of the study area (Figure 4) .
Drainage and Watershed
There is no major river draining through this taluk. Korampallam odai is a small natural channel draining the taluk. It flows from west to east and this odai is the main source for both agriculture and domestic purpose in this taluk. Korampallam tank is an important source of irrigation. The natural drainage network in the taluk area is endowed with good drainage pattern. In the city proper, the texture and density of the drainage are very low. The delineation of watershed has been done adopting the system followed by watershed atlas, All India Soil Survey and Land Use Organisation, Government of India and using Survey of India Toposheets. The study area has been classified as sub-watershed, mini-watershed and micro-watershed. The sub-watershed is approximately of the order of 30-50 sq.km, mini-watersheds of the order of 10-30 sq.km and micro-watershed of the order 5-10 sq.km. The watershed map (Figure 5) shows that there are 2 sub-watersheds, 5 mini-watersheds and 17 micro-watersheds in this taluk. Overall runoff rate in the taluk is vary from 8.0% to 18.50%.
Results and Discussion
Water Resource Status Assessment
The vectorised theme maps have been taken in Arc-Info GIS as input coverages. The union coverage of all these layers and its attribute table were used in Arc View GIS environment for table criterion analysis. Criterion is the definition of a relationship amongst the different parameters in commensurate terms i.e. expressing the different parameters in the same units or scale (Mukund Rao 1994). The table criterion has been prepared with all possible combinations of categories of different themes of layers (Table 1) . It is basically a matrix of theme categories and the solution class categories. Through, overlay analysis of vectorised theme maps of geology, geomorphology, soil, drainage, water quality and slope have been incorporated into as Arc-Info GIS input layers. The union coverages of all these layers and its attribute table were used in Arc View-GIS environment for table criterion analysis. A criterion Table 1 has been prepared with all possible combinations of categories of different themes of layers. The resource parameters of four layers have been ranked into five units which represents the water resources status of excellent, good, moderate, poor and very poor. This ranking was made based on their runoff percentage, groundwater prospects, water holding capacity and nature of the slope for water flow etc. These five water resource status class have been used for the purpose of resource status assessment of the study area.
Class I includes categories of quaternary alluvium in geology, buried pediment deep and flood plain in geomorphology, hydrologic soil group `A' in soil and 0-1% of slope in slope map. This class may be attributed to have excellent water resources for further developments.
Class II includes categories of Cuddalore sand stone and pluvio-marine sediments in geology, buried pediment medium in geomorphology, hydrologic soil group `B' in soil and 0-1% of slope in slope map. This class may be attributed to have good water resources.
Class III includes categories such quartzite in geology, buried pediment shallow, coastal plain and eolian plain in geomorphology, hydrologic soil group `C' in soil and 0-1% in slope map. It may have moderate water resources.
Class IV includes categories such as marine formation in geology, pediment, buried pediment and pediment inselbergs in geomorphology, hydrologic soil group `D' in soil and 1-3% of slope in slope map. It may have poor water resources.
Class V includes categories such as salt flat, mud flat and spit in geomorphology, hydrologic sub soil group-puot in soil and 3% and above in slope area, no categories have been represented in geology. This class may be attributed to have very poor water resources.
In this study, high significance is given for geology than other themes for water resource status analysis. Attribute data of the groundwater level have also been referred to during the analysis process.
Table 1 Criterion Table for Water Resources Assessment
|I Excellent||II Good||III Moderate||IV Poor||V Very Poor|
|Geology||Quaternary alluvium||Cuddalore sand stone and Fluvio-marine sediments||Quartzite||Marine formation* and Hornblende biotite gneiss||–|
|Geomorphology||Buried pediment deep and flood- plain||Buried pediment medium||Buried pediment shallow, coastal plain and eolian plain||Pediment buried pediment and pediment inselbergs||Spit*, salt flat* and mud flat*|
* Marine formation in geology theme and spit, salt flat and mud flat in geomorphology was included in poor and very poor water status classes (IV and V), respectively, because of its high saline nature of water.
Fig. 6 Water Resource Status
Most of the categories are classified based on this criterion rule. Some categories of union layers are not classified, to rectify these errors, each polygon has been selected and their respective status classes have been entered in its attribute table in Arc/GIS View environment. Urban settlements, river and tanks have been grouped under unclassifiegory (Figure 6).
The study area comprises of a very moderate area of good water resources. The villages in the middle part of Sankarapperi, northern part of Milavittan-I, Ayyanudaippu, Korampullam, Viranayakampathi, part of Mullakkadu-II, Kuliyankarisal, Servaikkaranmudam and southeastern part of Pudukkottai have good resources. Moderate water resources occur in the villages of Mappillai urani, eastern part of Sankarapperi, southeastern part of Milavittan-I, Maravanmadam, southern part of Pudukkottai, Kuttudankadu, Allikalam, middle part of Umarikottai and southern part of Perurani, southern part of Varthagareddipatti, Mudivittanendal, Kottalangulam and eastern part of Mullakadu I and II. Remaining villages on the northern part of Sankarapperi, northern part of Milavittan-I, northwestern part of Ayyanudiappu, Vadakkusilukkanpatti, Muthuswamipuram, Terkusilukkanpatti, Keltattaparai, Meltattaparai, major portion of Umarikottai, Dalavaipuram, Ramaswamipuram, northwestern part of Perurani, Timmarajapuram, western part of Verttagareddipatti and Mudivittanendal, middle and south eastern part of Mullakadu-II, and southeastern part of Milavittan-I the land and water resources are poor.
Evidently, the study area has witnessed much change owing to urbanisation and industrialisation (land use / land cover). The fall in agricultural area is indicative of displacement of rural population in the study area, forcing them to look for alternate sources of livelihood in the urban area. The results show that the available status of resources and its spatial distribution is limited. Nearly 50% of the geographical area has good to moderate resources. Moderate to poor land and water resource areas need to be reclamated to restore and improve its resource status. Coastal and marine pollution need to given more attention in the study area. Unplanned developments are further lead degradation of common pool resources in the region causing more hardship to the poor who have traditionally been dependent on these resources. Over coming all these problems still there is land and water resources to sustain human beings. Scientific approaches for resource management planning have been suggested.
Management Planning Strategy
Resource Management and Planning (RMP) strategy may be defined as a proactive or preventive measure that would maintain the good condition of the resource for a variety of long-term sustainable uses. The following management planning strategies will restore the resources and improve the status for sustainable future.
Intensification of agriculture in Viranayakkanpatti, Kuliyankarisal, Korampallam, Servaikaranmadam and Ramachandrapuram, has been accompanied by many changes. Lowering of groundwater leads to destruction of soil and cause gradual salinisation. In an ideal case, the irrigation water should be distributed, with a minimum of loss during its transportation. Improvements in the existing agricultural system can be achieved with a few "rules-of-thumb", for example.
- Making a careful plan of upcoming irrigation needs.
- Exploring the possibility of adding nutrients to the irrigation water.
- Intensive agriculture could be minimised.
- Using site-specific sprinklers for efficient delivery of water to plants.
- Construction of artificial irrigation canals with hydro-solution in each trench.
- Soil reclamation required urgently to Melthattaparai, Kelthattaparai area.
- Applying minimum amount of pesticides, including tillage and crop rotation
- Introducing non-chemical methods of pest control.
- Recreating of natural-meandering flow patterns of streams and rivers.
- Introduction of buffer zone close to the water courses.
Lowering of the groundwater table, salinity increase along the coastal areas and in some interior places of the region and the general groundwater decline all over the Thoothukudi taluk may be attributed to the continuous pumping of groundwater for agricultural, industrial and domestic purposes. The following measures will reduce the groundwater problems:
Deepening and modernisation of tanks in Thoothukudi taluk. Evicting the encroachments in the foreshore area of tanks and rivers. Rejuvenation of link channels to tanks both as feeders and surplus lines.
Artificial recharge programme or diversion of excess river water and tank water from one basin the other. Conversion of temporary diversion works into permanent structures.( Diversion structure)
Across Ayyanarodai to Abishegapakkam near Melathattaparai and Umarikottai area need checdams.
Improvement of dead storage by construction of ditches in the tanks.
Administrative control of groundwater by introducing minimum spacing of tube wells
Improvement of drainage facilities in the coastal area to avoid water logging.
Farm development works construction of recharge ponds, to improve better water recharge, especially in the mining areas of major tanks.
If the above suggested strategies are activated in the study area sustainable water resource management could be achieved.
Author expresses his acknowledgement to the Council for Scientific and Industrial Research, New Delhi for provided financial assistance during this study at Institute of Remote Sensing, Anna University, Chennai, India.
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