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Estimation of Groundwater Potential Zones Using Remote Sensing and GIS and Mapping ITS Quality



Shahzia Nargese
Student of Bachelor of Engineering in Geoinformatics,
Institute of Remote Sensing, College of Engineering- Guindy,
Anna University, Chennai
Mail id: shaz_ceg@yahoo.com


Vignesh Venkatasubramanian
Student of Bachelor of Engineering in Geoinformatics,
Institute of Remote Sensing, College of Engineering- Guindy,
Anna University, Chennai
Mail id: vickypicky2004@yahoo.co.in



C.Charles D. Richardson
Student of Bachelor of Engineering in Geoinformatics,
Institute of Remote Sensing, College of Engineering- Guindy,
Anna University, Chennai
Mail id: ccd.richards@gmail.com


Introduction

1.1 General
In many parts of the world, groundwater abstraction has exceeded the safe yield, resulting in overexploitation and overstressing of the aquifer. Therefore the quantum of available groundwater resource has to be assessed accurately for its optimum extraction and utilization. Groundwater crisis has been caused by human actions and demand for water in domestic use, agriculture and industry.

1.2 Groundwater contamination and its pollutants

Groundwater may be contaminated due to improper disposal of liquid wastes, defective well construction and failure to seal the abandoned wells. These provide possible openings for the downward movement of water into subsurface formations without the process of natural filtration. Contaminated groundwater may appear clear and may yet contain pathogenic organisms and pollutants, namely, pesticides, nitrates and TDS sources.

Tanners use a large number of chemicals and they discharge them into the rivers. The discharged effluents are stored in large lagoons and pollution occurs as the dissolved salts percolate the surrounding soil and enter into the groundwater sources.

1.3 Groundwater modeling
The use of groundwater models is prevalent in the field of Water Resource Engineering. Models have been applied to investigate a wide variety of hydro- geologic conditions. In general, models are conceptual descriptions or approximations that describe physical systems using mathematical equations; they are not exact descriptions of physical systems or processes. By mathematically representing a simplified version of a hydro geological system, reasonable alternative scenarios can be predicted, tested, and compared. Groundwater models describe the groundwater flow processes using mathematical equations based on certain simplified assumptions. These assumptions typically involve the direction of flow, geometry of the aquifer, the heterogeneity or anisotropy of sediments or bedrock.

1.4 Need for the study
Tirupur is a dry, water-scarce region, and the rapid expansion of the textile industry has taken place in an unplanned manner, with no associated development of supporting infrastructure or institutional capacity. Tirupur is facing the problem of environment pollution because of its dyeing industries. Textile production, particularly dyeing and bleaching, can be water intensive and can generate large quantities of effluents. Application of existing groundwater models helps in gaining knowledge about the quantitative aspects of the unsaturated zone and simulation of water flow in the saturated zone including river-groundwater relations, assessing the impact of changes of the groundwater regime on the environment, setting up/optimizing monitoring networks, and setting up groundwater protection zones.

1.5 Scope of the study
In the study area, the groundwater extraction is more due to textile industries. In order to avoid further depletion, there is need of micro level planning in this area. Also there is a need for estimating the groundwater quantity in order to take necessary development plans. Demarcation of groundwater protection zones is necessary to protect the zones which will act as recharge zones for the aquifer. These zones will be considered as sensitivity zones and the following activities such as the groundwater extraction beyond safe yield, the effluent discharge and the construction of barriers in those zones should be avoided for better management of an aquifer.

1.6 Objectives

The objectives of the study are

  1. To characterize the hydro-geological conditions of tirupur.
  2. To estimate the ground water quantity of tirupur.
  3. To demarcate groundwater protection zones.
  4. To determine the quality of noyyil river basin.
Review of Literature

2.1 General Concepts

Application of Geographical Information System (GIS) in groundwater modeling, groundwater quantity assessment methods the demarcation of groundwater protection zones are reviewed.

2.2 Groundwater modeling softwares

Kumar C. P. (2003) reviewed the available groundwater modeling softwares.

MODFLOW (Three-Dimensional Finite-Difference Ground-Water Flow Model).MODFLOW has become the worldwide standard ground-water flow model. MODFLOW is used to simulate systems for water supply, containment remediation and mine dewatering. When properly applied, MODFLOW is the recognized standard model.

Samuelson and Alan C, (2004) their study was undertaken to improve understanding of the geologic and hydro geologic framework of Delaware County, Indiana. Arc View GIS 3-D and Spatial Analysts along with VISUAL MODFLOW were used to study ground water flow patterns by developing a 3-D model of major aquifers. Areas of upward and downward gradients implied from differences in static water levels in shallow versus deeper wells are compared with areas of higher versus lower recharge in different soil associations and with flow paths in the model.

Bharati (2004), has simulated ground water flow for Nandanam area using visual MODFLOW. The volumetric budget for the model was checked and changes in storage of ground water system was assessed.

2.3 Groundwater Quantity Assessment

Shasidhar(2000), has developed GIS based ground water assessment model to estimate the ground water potential in a sub water shed in ambur minor basin in upper palar basin. MODFLOW was used to simulate the ground water flow in aquifer system.

Srinivas Rao.k, (2002), has created the database (i.e. Spatial and Non-Spatial database) and imported into ARC/INFO as coverage. The required non-spatial database is attached to respective coverage. The module selects the relevant coverage’s and calculates the recharge or seepage of individual component/coverage. The module then combines the results of individual components and displays value of Groundwater Balance and the categorization of the watershed.

Manoj (2002), has assessed the ground water potential of both command area and non command area of Thirukkazhukkundram block using water table fluctuation method. Visual MODFLOW was used to simulate the water levels in the wells.

2.4 To demarcate groundwater protection zones

Md. Mizanur Rahman and Shamsuddin Shahid (2004), have demarked ground water protection zones by using MODFLOW. From the groundwater flow model the software computes protection area around the water-well in three main steps, namely,
  1. Compute the zone of influence
  2. Compute the zone of contribution for a User-defined time period
  3. Combine both zones to demarcate the protection area.
Study Area details

3.1 Study area description
The area selected for this study was Tirupur block and the study area is bounded by Palladam taluk and Pongalur block in south, Avinashi taluk in west and Erode district in north and east, and consists of 23 villages. Slope varies from 0 to 3% where most of the area has slope less than 1%, so it is almost a flat. The block is drained by Noyyil River, and Nallar River.

Study area is situated between 11°N to 11°20' N Latitude , 77°10’E to 77°30’ Longitude. Tirupur block is situated at 50 Km. East of Coimbatore and the Municipal area of the block is spread over 27.20 Km2.

3.2 Soil Types
Soil types in Tirupur block can be divided into Fine, Fine loamy, Loamy skeletal, Clayey loamy and none/absent.

3.3 Geomorphology
The geomorphologic characteristics of Tirupur are broadly classified into Pedi plain, Habitation mask and Water body mask.

3.4 Land Use
The land use categories are classified as Built up, Agriculture, Water bodies and Waste land.

3.5 Slope
Slope of Tirupur can be divided into habitation mask, water body mask, 0 to 1%, 1% to 3% and 3% to 5%.

3.6 Rainfall
The yearly rainfall (in mm) for tirupur block is

1997 =435.1
1998 =448
1999 =879.5
2000 =794.2
2001 =646.4
2002 =506.2
2003 =709.1
2004 =475.7
2005 =1029.2

3.7 Geology
Geologically, hard rocks such as granite and gneiss with weathering depth varying from 1-19 m underlie the area. This formation was deeply weathered in the tertiary period. The study area consists of deep pediment along Noyyil river course from Sulur to Tirupur, shallow pediment along the stream courses joining Noyyil River.

3.8 List of observation wells in the study area:
  1. Andipalayam: 11.083°N , 77.0167°E
  2. Kaliyapalayam: 11.183°N, 77.383°E
  3. Nallur: 11.083°N, 77.4°E
  4. Mangalam: 11.0912°N, 77.26945°E
  5. Tirupur: 11.0916°N, 77.3527°E
  6. Perumanallur: 11.2055°N, 77.3541°E
Methodology

4.1 Ground water assessment
Water level fluctuation approach is used to estimate ground water potential, as representative data on seasonal water level fluctuations in the observation wells of the study area is available.

The ground water storage is estimated using the relation,

Ground water storage = Rise or fall in water level (m) x polygon area (m2)

x Specific Yield
4.2 Visual MODFLOW
Visual MODFLOW simulates ground water flow in aquifer systems using block centered finite difference method. In this method, an aquifer system is divided into rectangle blocks by a grid. The grid of blocks is organized by rows, columns and layers and each block is commonly called a cell. For each cell within the volume of the aquifer system, aquifer properties and information related to wells, rivers and other inflow and outflow features are specified. MODFLOW uses the input to construct and solve equations of groundwater flow in the aquifer system. Steady state and transient flow can be simulated in unconfined aquifers and confining units.

4.3 Demarcation of Ground Water Protection Zones

The following maps are used to demarcate groundwater protection/ sensitive zones in tirupur block :
  1. Geomorphology
  2. Land use
  3. Soil
  4. Slope
1)Geomorphology

  1. Pedi plain = 7
  2. Water body mask = 1
  3. Habitation mask = 1
2)Land use

  1. Water bodies= 10
  2. Agriculture= 7
  3. Waste land= 5
  4. Built up= 3
3)Soil

  1. Fine= 10
  2. Fine loamy= 8
  3. Loamy skeletal= 6
  4. Clayey skeletal= 4
  5. None or absent= 2
4)Slope

  1. 0% to 1%= 9
  2. 1% to 3%= 7
  3. 3% to 5%= 5
  4. Water body mask= 1
  5. Habitation mask= 1
Weightages assigned to each theme is:

Geomorphology= 4
Land use= 3
Soil= 2
Slope= 1

Overlay analysis was done on these themes using ArcGIS 9.2 and sensitive zones were identified.

4.4 Assessment of groundwater quantity

4.4.1 Groundwater Potential
The observation wells are indicators to measure the periodical changes in ground water level. Quantum of recharge/discharge that had taken place in the aquifer has been assessed from the monthly water level fluctuation data. Dynamic ground water potential of the study area was computed using Theisson polygon method. Volume of water was computed by using the water level fluctuation method.


Fig 1. Theisson polygons constructed for the six observation wells.


4.4.2 Ground Water Estimation Methodology
Using Theisson polygon constructed for each well the groundwater potential for the year 2003 was determined from the water level fluctuation, area of influence of each well and the specific yield. The total groundwater potential of Tirupur block for the year 2003 is 444824747 m3 / year.

4.5 Model Input
For each cell within the volume of the aquifer system, the properties were specified. Also, details relating to wells, rivers, other inflow and outflow features for cells were specified for model run.

4.5.1 Model Geometry
The extent and elevation of the area are modeled, grid layout, position and number of layers were defined. The total area considered for the model was 37142m x 51793 m. The grid size is 50 x 47.

4.5.2 Hydro-geologic Input
The hydro-geologic input parameters are collected from CGWB for the aquifer. These are in terms of hydraulic conductivity, specific yield, porosity, hydraulic conductance and recharge

4.5.3 Boundary Conditions
Each model requires an appropriate set of boundary conditions to represent the system’s relationship with the surrounding systems. In the case of groundwater flow model, boundary conditions will describe the exchange of flow between the model and the external system. The river boundary condition is used to simulate the influence of a surface water body on the groundwater flow. The surface water bodies such as rivers, streams, lakes and swamps may either contribute water to the groundwater system, or act as groundwater discharge zones depleting on the gradient between the surface water body and the groundwater system.

4.5.4 Recharge
Most commonly, recharge refers to aerial recharge which occurs as a result of precipitation that percolates into the groundwater system. However, recharge from sources other than precipitation, for example, artificial recharge can also be simulated.

Since natural recharge enters the groundwater system at the ground surface, visual MODFLOW only allows recharge values to be assigned to top layer.

Water level Fluctuation Method
This is an indirect method of deducing the recharge from the fluctuation of the water table and this method is widely used in India. The rise in the water table during the rainy season is used to estimate the recharge, provided that there is a distinct rainy season with the remainder of the year being relatively dry. The basic assumption is that the rise in the water table is primarily due to rainfall recharge.

Recharge =Difference in water level x specific yield

= 0.92 m x 0.1 x 1000
= 92 mm/yr

4.6 Assessment of groundwater quality
Six wells distributed along the noyyil river basin were observed and tested for quality. Theisson polygons were constructed (Fig 1) and well water quality data for 2002,2003 and 2004 were used to obtain the model using MODFLOW. The input data consisted of the quantity of Cl, Ca, Mg, Na, K, HCO3, SO4, CO3, F, NO3 , TDS, Hardness, Conductivity and Ph in the groundwater samples.

Results and discussion

5.1 General
Visual MODFLOW is the most complete and easy to use modelling environment for practical applications in three-dimensional groundwater flow and contaminant transport. Simulation is a technique used to evaluate feasible changes in a system and to seek those changes which improve the system according to some criteria and this help to choose the best solution among those studied. Several objectives or goals for better management of groundwater resource can be analyzed with the model simulation techniques.

5.2 Groundwater system of Tirupur

5.2.1 Water Level
The water levels in observation wells located across tirupur block ranged from 44.6m to 16.32m with the average difference between the highest and the lowest level in the wells being 4.4733m.

5.2.2 Ground Water Flow
The groundwater flow pattern is towards east of the study area up to river noyyil and southern and northern parts. The flow is away from the river and towards the canals and wells. From the flow pattern, it is clear that all the wells are the drainage areas and the river and both canals act as drainage during simulation period. It is also observed that from the size of the arrows, the velocity is relatively high at north eastern parts of the study area along the boundary of the river.


Fig 2. Groundwater flow directions for 2003


5.2.3 Demarcation of sensitive zones for tirupur block


Fig 3. Sensitive zones in tirupur block


High= Good recharge zone/ High sensitivity to pollution
Moderate= Moderate recharge zone/ Moderate sensitivity to pollution
Marginal= Marginal recharge zone/ Marginal sensitivity to pollution
Poor= Poor recharge zone/ Low sensitivity to pollution

5.2.3 Demarcation of sensitive zones for tirupur block


Fig 4. Groundwater quality assessment of noyyil river basin using MODFLOW


Tirupur block is a part of noyyil river basin and is highly polluted. This can be clearly seen in red color in the fig 4.

Summary and Conclusion

4.5 Summary
Groundwater flow for Tirupur Block was simulated using visual MODFLOW version 4.1. The aquifer characteristics, water level data for the observation wells were used as model input. The output from the model helps in understanding the groundwater system and determining the recharge required to improve the groundwater storage. The demarcation of protection zones was done by using overlay process and by giving weightages to the each theme in ArcGIS environment. The groundwater quality was mapped for the noyyil river basin using MODFLOW. The tirupur region was mapped as highly polluted.

4.6 Conclusion
In this paper, a sincere attempt was made to estimate the groundwater quantity of tirupur with the latest data available and to demarcate protection zones. An attempt was also made to map the quality of groundwater in the noyyil river basin.

6.3 Recommendation for future study

  • Similar attempts may be made for any other aquifer to understand and improve the groundwater potential.
  • Studies of micro level study areas may give accurate and reliable results than that of macro level study areas.
  • Study of optimal recharge quantity required to remediate the groundwater quality can be taken up.
  • Soil, Slope, Geomorphology and land use themes were considered for demarcation of sensitive zones. Further studies can be taken up by using several other themes as well.
  • Latest satellite images can be used for latest land use patterns.
References

  1. Bharati (2004), ‘Groundwater Modelling For Nandanam Area’, M.E. thesis, Anna University.
  2. Manoj.N. (2002), ‘Groundwater assessment model using GIS’ , M.E thesis CWR, Anna University.
  3. Kumar, C. P. (1997), ‘Estimation of groundwater recharge using soil moisture balance approach’, journal of applied hydrology, vol.243, pp.149-161.
  4. Parameswari.R (1998), ‘Groundwater modeling for Palar sub-basin’ , M.E. Thesis, CWR, Anna university.
  5. S.Pitchaikani (2007), ‘GIS and DRASTIC Modeling for assessment of groundwater vulnerability to pollution’, M.E Thesis, CWR, Anna University.