Water Resource (groundwater resource) Mapping Using Remote Sensing and GIS: A Case Study of Bhubaneswar, Orissa, India


Ms. Priyanka Mishra
Ms. Priyanka Mishra
B.Arch, M.U.D.P. (Master of Urban Development Planning)
Planning Officer, Delhi Development Authority, New Delhi.
Member of Winning Team – Map India Best Poster Award,2004.

ABSTRACT
Groundwater being hidden is more vulnerable to hidden threats of contamination and depletion.

Urban growth and rapid increase in population have induced tremendous pressure on natural resources. A common factor to most urbanisation is that it results in impermeabilisation of a significant proportion of land surface, and contamination of Groundwater. Urbanisation causes major changes in the frequency, volume and quality of recharge, although these changes cannot be measured directly and are thus difficult to quantify. Uncontrolled groundwater abstraction may lead to an imbalance in Ecosystem by not only decline in aquifer water levels, but also reversal of groundwater flow directions, land subsidence, saline water intrusion in fresh resources and induced pollution. Increase in nitrate contents in urban areas as a result of lack of adequate sewage disposal system is seemingly a burning issue. The increase in nitrate consumption leads to ‘blue baby syndrome’ in babies that may result in their death.

Introduction
The remote sensing & and GIS tools have opened new paths in urban development and water resources studies. Temporal data from remote sensing enables identification of groundwater aquifers and assessment of their changes along with the land use changes, whereas, geographical information system (GIS) enables integration of multi-thematic data. The concept of integrated remote sensing and GIS has proved to be an efficient tool in integrating urban planning and groundwater studies that would open new vistas for planning for urban areas in an eco-friendly way.

Study Area
The capital city of Orissa- Bhubaneswar, its name derived from Sanskrit word ‘Tribhubaneswar’ meaning the God of Universe- Lord Shiva, is located between 20012’N and 20025’N latitudes and 85044’E to 85055’E longitude on the western fringe of coastal plain across the main axis of Eastern Ghats in Khurda district of Orissa. The city has witnessed a dynamic change in growth of population. The city designed for a population of 40,000 in 1954 with an area of 1684 Ha holds as many as 6,57,477 (2001 census), which is expected to increase to 16,87,087 by 2031. The present City sprawls over 233sq.km comprising of total 2312 revenue villages. The shape of the city is almost dumble shape. Its boundary in the south, southeast and east are somewhat irregular. The city is divided into 30 wards under the Bhubaneswar Municipal Corporation control. There are 204 more villages along the rural periphery, which are also coming under the direct sphere of influence of the city. As a result there is tremendous pressure on resources as groundwater. Although the city lies on the western side of the Mahanadi Delta on the bank of river Kuakhai, a distributory of Mahanadi along with River Daya, branching off from Kathajodi that flows along the southeastern part of the city, 35% of water supply depends heavily on dugwells and borewells.

Bhubaneswar enjoys a salubrious and moderately equable humid tropical climate with average maximum temperature around 38oC and average minimum temperature of 16 oC. Bhubaneswar receives about 120 cm of rainfall during southwest monsoon (June to September), which contributes to about 75% of the annual rainfall. Southwest monsoon generally arrives over Bhubaneswar by second week of June and prevails up to second week of October. During this period, more than 45% are rainy days. The relative humidity varies from 48 to 85%.


Fig 1Location Map of Bhubaneswar, Orissa


Topography
Bhubaneswar lies on the western fringe of the mid-coastal plain of Orissa with an average elevation of 45m above the main sea level. It lies on the low lateritic plateau and the erosion has made its topography a valley-and-ridge one. The area can be divided into two broad physiographic divisions, namely, (a) the Western Upland and (b) the Eastern Lowland. The general slope of the land is from the west to the east, south and southwest. Most of the areas lying in the east and southeast along the three rivers have an average slope below 1°. The areas lying in the middle and northwest have an average slope ranging from 1.50° to 2.0°.

Geology
Geologically the Bhubaneswar region belongs to the Gondwana landmass, one of the oldest and most stable landmasses in the world. So the rocks range from the Archaean to the recent period. But the major part of the area is covered with the quaternary alluvium and lateritic soil.

Hydrogeology
Upper Gondwana rocks are grouped as the semi consolidated formations; the older and the younger Alluviums, which occur to the east of the city, are the unconsolidated formations. The depth of water table ranges from 5-12m in the Laterites and the weathered sandstones to 40-150m in the fractured and friable sandstones forming the deeper aquifers that are under semi-confined to confined conditions. The rock types in and around the western parts of the city store water recharged by rainfall. The recharge may dwindle in future as urbanization crawls further.

Database
SoI topomaps (73 H/11, 73 H/12, 73 H/15, 73 H/16) in the scale of 1:50,000 were used to prepare the reference map for the study area with supplementary information from Airphoto Data and satellite images (SPOT Kpan Data (1990) and IRS-1C PAN Data (1997). The database for hydrogeomorphology was prepared with the help of ORSAC, Bhubaneswar. Water Table Fluctuation, Pre-monsoon and Post-monsoon water level data along with Water Quality Data were procured from Central Ground Water Board and Ground Water Survey and Investigation, Bhubaneswar.

Analysis
Depth to water level: The deeper water levels are mostly observed in the western part of Bhubaneswar and shallow water levels from eastern part of the city along the rivers in the flood plain. The depth is maximum upto 6m bgl in December that falls to 8m bgl in May. The trend of level of groundwater in last decade i.e. from 1990 to 2000 shows that both fall and rise in groundwater levels are restricted within 0.5m that indicates there is no significant change in groundwater regime quantitatively during these 10 years (Fig 2). However, there are enough reasons for a greater decline in next two decades.


Fig 2 Depth to Water Level, May 1998        Depth to Water Level, Dec 1998


Groundwater Quality
High quantity of Nitrate (>45mg/l) has been found at few places in the city. The nitrate content in the wells has increased beyond permissible limits in last decade (Fig 3). The shallow groundwater is vulnerable to contamination under macro-pore flow conditions through laterites and alluvium. Seepage from septic tanks/ cesspools in lateritic formations poses threat to potable water of phreatic aquifers in near future. Iron is present in low concentration in dug wells but some of the tube wells and hand pumps are found to have high Iron content that further increase in summers as the lever of groundwater recedes.


Fig 3 Groundwater Quality in dugwells


Urban Development
The lack of sewerage system results in flow of sewage into the natural drains. Moreover, untreated effluent from the septic tanks in the individual premises, overloaded due to lack of any maintenance, is discharged into the natural drains. High porous formations like laterites and permeable deposits like alluvium can transport some of the pollutants to the aquifers below. Sandstones with low porosity and permeability are more conservative for the download movement of the pollutant plume.

Urban Development and Generation of Sewage
The consumption of water in the city is 89MLD, generating 71MLD of sewage daily. Out of this 57MLD (80% of total sewage) sewage is flowing through open drains/ nallahs passing through the city degrading the environment as well as the ambience of the city. The adverse impact of the urban development has resulted in pollution of water bodies of the city. Development activities near the wetland and upcoming of buildings add fuel to the fire. To avoid the worst situation of contamination of water resources, the city needs to have sewerage system in totality and effluent should be discharged into the water bodies i.e., river or nallah only after the primary and secondary treatment.

Urban Development And Open Spaces
A considerable portion of the ground is covered with relatively impermeable layers of various paving materials; infiltration and evaporation are too less and most precipitation runs off. The development of new colonies takes form of small campuses in the fringe areas. The plot sizes are decided such that developer’s great mileage in terms of built up area.

  • The buildings constructed cover nearly 70% of the plot area with minimum setbacks. Moreover, 80% of remaining 30% is paved by impermeable materials as parking, plinth protection, etc. Thus, the development results in hardly 10% of unpaved area to percolate rainwater.
      • 10% open area, which is essential as per the norms, if provided, is also paved up to 50%.
  • The increasing needs of stones for construction has left many abandoned laterite quarries and low lying depressed areas, which are being used as solid waste disposal sites of the city.

This gives a clear picture of system of urban development. These colonies are dependent purely on groundwater, in most cases, each plot having its own bore well or dug well. Open areas left for recharge by rainwater is left to merely 10% of the total developed area. The situation calls for immediate attention as the rte of abstraction exceeds recharge to a great extent.

Discussion

Hydrogeomorphology, Lineament & Drainage:

Hydrogeomorphological map was prepared from remotely sensed data. The hydrogeomorphological features, present in study area were classified into (i) flood plain, (ii) alluvial plain, (iii) Valley Fills, (iv) Laterite Uplands, (v) Moderate weathered buried Pediplain (BPPM), (vi) Shallow weathered buried Pediplain (BPPS), (vii) Buried Pediment (BP), (viii) Pediment, (ix) Denudation Hill and (x) Residual Hill (Fig. 4).

The city has an undulating ridge and valley topology covered by number of natural drainage channels. The drainage is controlled by the River Kuakhai on the north and River Daya in the south. There are 12 major drainage channels along with a number of open drains running west to east crisscross the cityout of which 10 are identified as drainage zones on planning document.


Fig 4 Hydrogeological Map of Bhubaneswar


Most of these finally join to form Gangua Nallah that meets River Daya. It has been stated that no development will be allowed in this zone, however, rapid development in this zone is causing flooding in upstream, water pollution, water logging and other hazards.
The major directions of the lineaments are from W-S and N-W.

Groundwater prospects map has been generated by integration of hydrogeomorphology, lineament, and slope (Fig. 5). The groundwater prospects zones were delineated as excellent, very good, good, moderate and poor.


Fig. 5 Groundwater Potential Map of Bhubaneswar


II. Sewage System For The City
As per 2001 census population of Bhubaneswar city is 6.57 lakhs. The designed population has been worked out to 16.9 lakhs by the year 2031. For this population, the total requirement of water @150 lpcd will be 253 MLD. Considering 80% of the total water supply as sewage, the sewage, which will have to be collected and treated, will be to the tune of 202.45 MLD.

Proposed Project
The city of Bhubaneswar has been divided into two zones depending upon the topography and the drainage pattern of the area. These zones along with the proposed location of the sewage treatment plant are shown in Fig 6.


Fig 6 Sewage Zones of Bhubaneswar


a. Zone 1 - North Zone
The municipal wards included in this zone are 1, 2, 6,7,8, and 17. The zone also partially includes Wards 3, 4, 13, 14, 16 and 18 (Table 8.1), generating sewage upto 32MLD
The population of the zone is 2.9 lakhs and is expected to reach 6.76 lakhs by the year 2031.

b. Zone 2 - South Zone
This zone mainly comprises of Old Town area, Bapuji Nagar, Satya Nagar, Forest Park, BJB Nagar, Siripur, Baramunda, Khandagiri, Aiginia, Pokhariput.
The population of the zone is 3.6 lakhs, generating sewage upto 39MLD and is expected to reach 10.14 lakhs by the year 2031.

The capacity of the treatment plants has been estimated as 90 MLD or 18750 litres (for 30 minutes) and 113 MLD or 23540 litres (for 30 minutes) as per the projected population of the Zone 1 and Zone 2 respectively.

The STPs would be able to cater to the needs of the city sewage till 2031 and later on can be expanded depending on the requirement. Ample land has been allocated for future expansion.
Site Selection Criteria
The selection criteria for the site involve various parameters that are as below.

1. Topography:
  • Best suitable land has been selected based on the topography of the city. The site is at lower level contours for easy flow of sewerage.
  • Minimum slope would prevent erosion.
2. Location:
  • The site is at a safe distance from the habited areas, i.e. more than 500m.
  • The site is located near the river for letting out the treated effluent.
  • Minimum inconveniences for repairs of system and new pipeline.

3. Availability of Land:
  • There is scope of land for future expansion.
4. Socio-Economic Aspects:
  • No change in adjacent property values.
  • No relocation of people is required.
5. Environmental Aspects:
  • Improved water quality without negative environmental impacts.
  • Some odors when switching from anaerobic to aerobic decomposition.
Application of Wastewater
  • Use of Sewage in Pisciculture;
  • Sewage Utilization in Forestry;
  • Use of Vermiculture for Waste Management (use of earth worms for bioconversion of wastes). This would yield fuel (methane fertilizer) and nutrient rich vermucasts;
III. Protection of areas contributing to groundwater recharge

i. Existing Reserved Forests/ Protected Forests
ii. Green Belts and Open Spaces
iii. Parks/ Organised Open Spaces
iv. Water Bodies, Lakes, Ponds And Natural Wetlands
  • Complete check on municipal sewage entering into the ponds, lakes and wetlands.
  • Complete drainage of existing water, desilting and cleansing of bottom debris and filling the tanks with fresh water. This would help in easy percolation of clean water for groundwater recharge.
  • Arrangements for regular flushing of fresh water in temple ponds with provision of outlet with filter.
  • Strict control on throwing of ritual offerings into the ponds.
  • Arrangements to provide Public Toilets in the vicinity of the ponds and connect them with the main sewer lines.
  • Attempts to clear algal bloom by mechanical means, suitable algaecide or introducing suitable fish varieties capable of scavenging biological, organic and inorganic loads of the ponds.
v. Open Drains/ Natural Drains
  • Further widening of the drains at some stretches to develop groundwater recharge areas or stagnant water pools;
  • Development of recreational zones along drains by providing pathways and landscaping along their banks;
  • Development of Reed Bed on natural drains to clean up the organic and inorganic matter;
  • A minimum of 50m belt along the drains to be protected from encroachment.
  • Different meeting places of the valleys with Gangua Nallah can be aesthetically developed with gardens and similarly the lower stretches of the nallahs.
RAINWATER HARVESTING

Bhubaneswar Urban Area and Rainwater Harvesting
The normal monsoon rainfall of Bhubaneswar city as per IMD received from June 15 to September 30 is 1200mm. For rainwater harvesting purposes, only normal monsoon rainfall is considered for easy management of the rooftop rainwater harvesting.

Table2 Assessment of rainwater for different individual rooftops for Bhubaneswar City



A small example of 20,000 residential buildings with rooftop area of 150sqm each along with 80,000sqm rooftop area of Government buildings is taken here.
Rainwater harvesting on rooftop would contribute to 6.48 MLD water for the supply. This amount of water is fair enough to supply water to 48000 people or 9600 households of 5 members @135 lpcd.

Rainwater Harvesting can be done successfully using Abandoned dug wells, Abandoned running hand pumps, Recharge pits or Recharge trenches.

Conclusion
Lack of proper infrastructure such as water supply and sewage treatment and disposal system along with lack of public participation in the so-called planned city has induced severe stress on groundwater both quantitatively and qualitatively. Besides widespread pollution of surface water, discharge of untreated wastewater in open drains and natural unlined nallahs that are important in groundwater recharge process and leachate from unscientific disposal of solid wastes make groundwater more vulnerable to contamination. The study indicates that the quality in few areas would deteriorate further in short period of five years, making it unfit for consumption. This would far increase the scarcity of water in the areas that are purely dependent on groundwater.

Groundwater environment is extremely sensitive and once degraded would take hundreds and even thousand of years to revive. Groundwater need not remain in the hands of a few to decide and plan about. Urban planners should have a better understanding of the importance of groundwater in urban planning and vice versa and plan a city in a “Water Friendly” way.