TO THE SPATIAL DISTRIBUTION OF GROUND WATER QUALITY FOR DIFFERENT ELEMENTS USING LEGACY DATA OF RWS & S , ANDHRA PRADESH , INDIA

The state of Andhra Pradesh, India falls in water stress area. The primary objective of this study is to examine the spatial distribution of different chemical elements with respect to its contamination level. About 70% of drinking water needs in rural areas and 40% drinking water needs in urban areas are met from groundwater resources. In the last decades, rapid population growth coupled with agricultural expansion due to subsidized power to agriculture has significantly increased demand on groundwater resources. Combined to this, the effect of Global warming has put stress on ground water which is resulting in declines in water levels and deterioration of ground water quality. This may be evidenced by the fact that the phreatic aquifer which was in use two decades ago, is existing no more now in some of the parts of the study area and the water is being drawn from deeper aquifers beyond phreatic aquifers. The study has been carried out for which one or more elements are contaminated and to study its spatial distribution. * Corresponding Author:Prathapani Prakash, Associate Project Manaager, Geosciences Division, APSRAC (prakashmhbd@gmail.com) 4 Water stress Annual per capita water supply for all uses is in between 1000 and 1700 m per person.


INTRODUCTION
Groundwater is a vital natural resource.It is estimated that approximately one third of the world's population use groundwater globally for drinking.In some parts of the world such as large areas of the southern India, groundwater is the unique source of water.In general, the state of Andhra Pradesh is characterized by scarcity of water and rapid growth in population.Water is therefore the most important constraint for future development in this region.However, it is anticipated that the process of development will continue, resulting in greater demands for fresh water and declining groundwater level.India as a country in the southern Asia is confronted by multiple water-related problems, such as drought and environmental degradation from overexploitation of aquifers in the southern and western parts of the country.
Understanding the groundwater quality is important as it is the main factor determining its suitability purposes.In the study area, it is observed that the extensive agricultural activities and urbanization resulted in the contamination of the aquifer in recent years.
The study has been carried out for the spatial distribution of following 6 elements contaminated in the study area: Fluoride (F), Chloride (Cl), Total Hardness (TH), Total Alkalinity (TA), Total Dissolved Solids (TDS) & pH.

STUDY AREA
The study area includes the undivided Andhra Pradesh state which is falling in the south eastern part of India with an areal extent of 2,75,068 Sq.Km.It lies in between longitudes 77 0 to 84.40 0 E and latitudes 12.41 0 to 22 0 N.

Physiographic of the Study Area
The State of AP is endowed with a variety of physiographic features ranging from hills and undulating plains to coastal deltaic environment.The state has three major river basins -Godavari, Krishna and Pennar.The climate in A.P. is semi-arid to arid.Geomorphologically, the state can be categorized into pedi-plains, coastal alluvial plains and hill ranges.
The state receives an annual rainfall of 940 mm on an average, with wide variations among the districts.It ranges from 1200 mm in Srikakulam District to about 550 mm in Anantapur District.The majority of the rainfall (66%) is received from the south-west monsoon during June-September, while the northeast monsoon (October-December) contributes about 25% of the rainfall.Major constraints are imposed by the spatiotemporal variations in water availability, though in aggregate terms, the water is sufficient to meet current demands in all but the driest years (FAO, 2004).

Geology & Hydrogeology of the Study Area
The State of AP is underlain by rock types ranging from Archaean to recent alluvium with varied texture and structure.Nearly 85% of the state, i.e., about 2.33 lakh sq km, is underlain by hard rock's -igneous, volcanic and metamorphic rocks, mainly Granites, Gneisses, Charnokites and Khondalites in the Eastern Ghats, Cuddapah (Middle and Upper Proterozoic), Kurnool and Deccan traps (Eocene).The remaining 15% of the area, i.e., 0.42 lakh sq km is underlain by soft rocks -Tertiary and Gondwana sandstones & shales and alluvium of recent age.Dolerite dykes, quartz reefs, feldspathic and pegmatite veins extending from a few meters to a few kilometers cut across the country rocks at many places.The dolerite dykes have been emplaced along major prominent fractures.The vertical joints in granites are also aligned to the major direction of fractures / lineaments.Fluorite and apatite rocks contain fluoride-bearing minerals and are the main source of fluoride in groundwater.
The groundwater quality varies from place to place and hence there may be pockets of better and usable groundwater in these poor quality groundwater areas also.

Soils
Soils play an important role in improving groundwater recharge.The soils of the state are broadly classified into red, black and alluvial.Red sandy soils cover the largest area in the state (67%) and occur widely in the Telangana and Rayalaseema regions.The black soils are in general transported by rivers.The deltaic alluvial soils, coastal alluvial soils and coastal sandy soils are formed by the riverine system.

Estimates of Groundwater in India
India with 2.4% of the world's total area has 16% of the world's population, but has only 4% of the total available fresh water.This clearly indicates the need for water resources development, conservation and their optimum use.At the aggregate level, India is not short of water.
As per the assessment of Central Water Commission (1993), the water resources potential of the country is estimated to be of the order of 1869 billion cubic metres (bcm), which includes replenishable groundwater that gets charged on annual basis.Within the limitations of physiographic conditions, sociopolitical environment, legal and constitutional constraints and the technology available at hand, the utilizable water resources of the country have been assessed at 1123 bcm, of which 690 bcm is from surface water and 433 bcm from groundwater sources (CWC-1993).Harnessing of 690 bcm of utilizable surface water is possible only if matching storages are built.
The annual replenishable groundwater resource for the entire country is 433 bcm.The overall contribution of rainfall to the country's annual replenishable groundwater resource is 67% and the share of other sources, including canal seepage, return flow from irrigation, seepage from water bodies and water conservation structures taken together is 33%.
In the state of AP, the contribution of other sources is more than the national average of 33%, mainly because of canal seepage and intensive irrigation.The southwest monsoon being the most prevalent contributor of rainfall in the country, about 73% of the country's annual replenishable groundwater recharge takes place during the kharif period of cultivation.Keeping 34 bcm as the allocation for natural discharge during the non-monsoon season, the net annual groundwater available for utilization in the entire country is about 399 bcm

Estimates of Groundwater in Andhra Pradesh
The state's total water resources, both ground and surface water are estimated to be about 108.15 bcm (3820 tmc) (about 9.5% of country), out of which about 62.29 bcm (2200 tmc) is currently being utilized for drinking, agriculture, industry and power generation purposes.The per capita annual water resources work out to be slightly more than 1400 cum, and the utilization is about 800 cum (AP Water Vision, 2004).The current percentage of withdrawal of available water in AP is 58%.By the year 2050, Andhra Pradesh will come in to the status of water "severe" state from the present state of water "stress".This calls for efforts towards efficient management supported by appropriate policy framework for appropriate water governance.

Groundwater Development in AP: A Spatio-Temporal Analysis
A recent expert group report (GoI, 2007) indicated that groundwater resources in the country are under severe stress.In 2004, an alarming 28% of the blocks in the country were in the category of semi-critical, critical or over exploited, compared to only 7% in 1995.This is clearly indicating the increase in water demand over a period of time.The rate of extraction far exceeds the rate of replenishment in many blocks, leading to a progressive lowering of the water table.

GEC Report of AP
Groundwater resource of the state is estimated on a regular basis by the MoWR in close collaboration with the Ground Water Department of Government of AP.As per the methodology followed, the status of groundwater is simply given as a ratio of the utilization and recharge, which is called the SGD.It can also be called the stage of groundwater utilization for clarity.
The assessment is done based on 1229 watershed assessment units spread across the state of Andhra Pradesh.There is a separate categorization for over exploited villages mainly used for A.P. state regulation.Recharge computations have been made separately for ayacut (command) and non-ayacut (noncommand) areas.It is observed that most of the groundwater development is confined to the non-ayacut areas.
On an average, the density of wells increased from five wells to over 10 wells per sq km.However, in hard rock areas, it is over 20 wells per sq km, while in some pockets it is as high as 100 wells per sq km.Consequently, well yields decreased considerably and water levels went down alarmingly.

Why is Water Quality an Issue?
Water resources management has often focused on satisfying increasing demands for water without adequately accounting for the need to protect water quality and preserve ecosystems and biodiversity.Rapidly growing cities and industries, expansion of the mining industry, and the increasing use of chemicals in agriculture have undermined the quality of many rivers, lakes, and aquifers.Poor water quality can create health hazards, threaten downstream irrigation areas; reduce industrial capacity through loss of hydropower production and costs arising from removing pollutants; destroy ecosystems; and affect biodiversity.If pollution makes the water unfit for human use, degraded surface and groundwater quality can even add to water shortages in water-scarce regions.
Maintaining good water quality is a growing concern in water resources management around the world.In developing countries, major water quality concerns include fecal contamination from the disposal of untreated or partially treated municipal and domestic wastewater into surface water bodies, and the increased use of pesticides, fertilizers, and herbicides in agriculture.Trace chemicals and pharmaceuticals, which are carcinogens and endocrine disrupters, are now seen as a water quality concern in the industrialized world.As these examples demonstrate, water quality issues depend very much on the context.Thus, chlorination of drinking water can introduce trihalomethanes, which are carcinogenic.
Even though water quality deterioration is often not as visible as water scarcity, its impacts can be just as serious with significant economic consequences.Health hazards, agricultural production losses, and losses of ecological function and biodiversity have long-term effects that are costly to remediate and impose real suffering on those affected.Sediments eroded from watersheds increase turbidity and reduce storage capacity in dams.

Key Water Quality Issues
Both natural processes and human activities can cause deterioration in water quality.Water quality standards have been developed to assess the suitability of water for drinking as per Bureau of Indian Standards Organization (ISO) 10500: 1991.
Contamination spread of element-wise distribution from a single element to 6 elements are plotted against to each habitation for pre and post monsoon seasons separately and its spatial distribution is studied using satellite remote sensing techniques and with respect to other collateral data as mentioned below: 1. Geology 2. Hydrogeomorphology 3. Groundwater Exploitation (GEC) Report 4. Forest layer 5. Irrigation Command Area Map 6. Ground water level map

Groundwater Quality Variations during Pre-Monsoon Season
The spatial distribution of elements contaminated during premonsoon season (Fig. 1) is plotted against to each habitation.In the map the distribution of fresh samples are also shown below the contaminated sources.It is noted that the fresh water is available along with the contaminated water in some of the patches.The following is the status of element-wise number of sources potable and or contaminated during the pre monsoon season: The following graph (Figure 2) shows the distribution of major contaminated sources with combination of different elements as against to total quality tested sources (1,05,505): Figure 2. Distribution of contamination elements

Groundwater Quality vs Groundwater Development during Pre-Monsoon Season
The spatial distribution of elements contaminated versus Ground water categorization is studied.From the study it is revealed that, the ground water quality is severely affected in Semi-critical, Critical and Over exploited zones as compared to Safe areas.

Ground Water Quality vs Ground Population during Pre-Monsoon Season
With the available data, the ground water quality versus population likely to be affected are studied for entire Andhra Pradesh.It is assumed that out a total population of 2.26 Crores covered, about 54 Lakh people are likely to be affected with at least one or more elements for entire A. P.

Groundwater Quality Variations during Post-Monsoon Season
The spatial distribution of elements contaminated during postmonsoon season (Fig. 3) is plotted against to each habitation.In the map the distribution of fresh samples are also shown below the contaminated sources.It is noted that the fresh water is available along with the contaminated water in some of the patches.The following is the list of number of elements contaminated against to total number of source(s) during post-monsoon season ( The following graph (Fig. 4) shows the distribution of major contaminated elements as against to total number of sources quality tested (26,492):

Ground Water Quality vs Ground water development stage during Post-Monsoon Season
The spatial distribution of elements contaminated versus Ground water categorization is studied and.From the study it is revealed that, the ground water quality is severely affected in Semi-critical, Critical and Over exploited zones as compared to Safe areas.

Ground Water Quality vs Ground Population during Post-Monsoon Season
With the available data, the ground water quality versus population likely to be affected are studied for entire Andhra Pradesh.It is assumed that out a total population of 73.12 Lakhs covered; about 16.24 Lakh people are likely to be affected with at least one or more elements for entire A. P.


The majority of sources of Andhra Pradesh are contaminated with Fluoride (geogenic), TDS (geogenic/anthropogenic) and Total Hardness (geogenic/anthropogenic).TDS & TH are out of range mostly in command areas.This could be because of extensive irrigation practised in command areas and recharge from the nutrient rich surface waters.


In the coastal command areas along with TDS & TH, there is contamination of Chloride as well.This may be because of sea water ingress, anthropogenic activity and over exploitation.Ingress of seawater into coastal aquifers as a result of over-extraction of groundwater will made water supplies more saline, unsuitable for drinking and irrigation.


The origin for fluoride contamination occurs geogenically.Fluoride in ground waters occurs because of fluoride bearing minerals present in the parent rock.When the fluoride is dissolved in ground waters because of chemical action with water, the concentration of fluoride is getting increased.The fluoride is existing naturally in higher percentage in the rocks of some of the areas of Andhra Pradesh.When we compare the fluoride contamination in A.P. with ground water exploitation areas, it occurs more severely in areas where it is in critical and over exploited areas.This could be due to over draft of ground water for irrigation, industrial and also for domestic uses.The erratic rainfall could have acted as catalyst for overexploitation when the deficit rainfall occurs.Because of over draft of ground water especially for irrigation, the areas are becoming contaminated with fluoride.If sufficient rainfall occurs and the draft is within the limits, there could have less contamination.


The

Figure 1 .
Figure 1.Map showing the spatial distribution of elements contaminated during pre-monsoon season

Figure 3 .
Figure 3. Map showing the spatial distribution of elements contaminated during post-monsoon season

Figure 4 .
Figure 4. Distribution of contamination elements

Figure 5 .
Figure 5. Aquifer Map of the study area

Table 1
. Status of percentage of elements contaminationIn the pre-monsoon season, if we put the order of districts which are having contaminated sources / elements, the following is the order of importance: Guntur, Prakasam, Kadapa, Ananthapur, Warangal, Khammam, Nalgonda, Kurnool, Nizamabad, Karimnagar & KrishnaThe following table shows the major contaminated elements out of total quality tested sources in Andhra Pradesh (Table2):

Table 2 .
Status of percentage of major elements

Table 4 .
Status of percentage of major elements vulnerable, as contaminated surface water can enter them quickly.In contrast, deep aquifers or those of less permeable materials are less vulnerable either because of the longer travel and filtering time or the overlying protective confining layers of rock preventing the downward migration of contaminants.
ground water quality problem is more severely observed in Semi-Critical, Critical & Over Exploited zones as compared to other safe areas. In Khondalites and Charnockitic terrain the ground water quality problem is existing especially in the districts of Srikakulam, Vizianagaram Vishakapatnam & part of East Godavari.The ground water quality problem is existing mostly in command areas for the elements Total Dissolved Solids, Total Hardness & Chloride. It is observed that in forested and safe areas the ground water quality problem does not existing.This implies that the natural cleansing is being done in forested areas and the quality is within permissible limits.