eChapters

Abstract

Aquifers are usually composed of permeable layers that can ways a considerable amount of groundwater. Usually, aquifer units are correlated through the concept of lithostratigraphy. For low-permeable aquifers, it is difficult to define the spatial distribution of hydrogeological units, and this study attempts to use geochemical methods to identify the groundwater flow paths in an area of Southeast coast of Tamil Nadu, India. Multiple geochemical analyses, including groundwater chemistry; stable isotopic compositions of d¹⁸O and 8D contents were performed.  Spatial distribution of d¹⁸O, dD, Cl-/HCO-₃ show that northeastern part of the study area seriously affected by seawater intrusion. The highly permeable aquifers at the east coastal region are characterized by high hydraulic conductivity as compared with other regions of the study area. Hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation-exchange reactions.

Abstract

Coastal aquifers are the sources of freshwater which are being over extracted due to increase in population, agriculture and industrial activities. This over exploitation has resulted in decline in groundwater level and intrusion of sea water into the coastal aquifers making it unfit for human utilities. An attempt has been made in the coastal tracts of Pondicherry region using Electrical resistivity imaging. The survey has been attempted in six locations spread thought the study area and the interpretation has been attempted by RES2DINV software. The profile length attempted was between 150 to 300 m with electrode spacings between 5 to 10 m. The apparent resistivity ranges between 0.1 to 1183 & ohm. Sea water intrusion was prominent along the northern parts of the study area and lower resistivity isolated in kirumambakkam has been interpreted as salinity due to the presence of clay minerals. In nallavadu saline intrusion has been identified at shallow depth.

Abstract

Deduction of overindulgence fluoride (F)  from the water has been endeavor by numerous investigators by using different materials both natural and artificial. The objective of this paper was to attempt the fluoride removal by using the locally available natural materials such as red soil, untreated charcoal, local powdered brick, fly-ash from Neyveli (thermal power plant) and mineral serpentine were used, adopting column method. Maximum defluoridation occurs immediately after the experiment has started. The morality of fluoride removed per gram is more in red soil when compared to the other materials. Variation of fluoride removal with time was studied after the erection of the column /unit, the defluoridation setup was then connected to the public water supply from the overhead tank of 50,000L capacity. Higher F removal was noted when flow rate was lesser. An attempt on the regeneration of the fluoride adsorbed soil was also made.

Abstract

A total of 30 groundwater samples were collected in four different seasons (Pre Monsoon, South West Monsoon, North East Monsoon and Post Monsoon) from the coastal aquifers of Kalpakkam region of Tamilnadu. The samples were collected covering the seasonal and lithological variations to infer the influence of natural geochemical processes and anthropogenic sources on the groundwater chemistry. The collected samples were analysed for the parameters like EC, pH and Major ions. The saturation index of silicates and carbonates shows that state of saturation to over saturation, but the sulphate minerals is dominantly under saturated. In the inverse modeling three models are obtained using PHREEQC and the error percentage is noted as 7.45%.

Abstract

The geochemical signature and vulnerability of groundwater of the East Coastal aquifers of  India from Pondicherry to Nagapattinam were determined. The coastal aquifers are fragile and this situation becomes more intense in aquifer systems like that of the Pondicherry to Nagapattinam region. A total of 136 water samples were collected during pre and post monsoon of 2008 and 2009 respectively. Out of which 45 samples for each pre and post monsoon from shallow groundwater and 23 samples for each pre and post monsoon from deeper groundwater.. The samples collected were analysed for major, minor cations and anions. Selected samples were also analysed for stable isotopes (d¹⁸O and dD). The analysed samples were studied for; their utility for different purpose, the nature of the geochemical classification, their variations in ion ratios, extent of sea water intrusion and the percentage of mixing, The study reveals that chief mechanism controlling shallow groundwater is the salts precipitated in the pore spaces during the Pre monsoon were leached and dissolved during the subsequent monsoon apart from sea water intrusion. Southern part of the study area  is more vulnerable than the Northern part of the study area.

Abstract

In semiarid climates, a significant component of recharge to basin aquifers occurs along the mountain front. In this scenario Mountain Front Recharge study has been carried along the foothills of Courtallam ,Tamil Nadu. A total of 53 groundwater samples were collected along the foothills and measured for major cations and anions using standard procedure. Saturation index (SI) of carbonate minerals like Aragonite,Magnesite, Calcite and Dolomite,LogpCO₂ and Ionic strength obtained from WATEQ4F output. pH plays a significant role in the saturation index of the minerals. Most of the Carbonate minerals shows undersaturation  with the pH range 7.5. Positive relationship between SI and HCO₃ is noticed. A sharp increase of pCO₂ values towards the foothills region suggests that the groundwater has been recharged by, acquiring longer flow path during its infiltration into deeper level near foot hill region. The SI of these carbonate minerals was spatially distributed to identify the areas of higher SI and also it is compared with the water level fluctuation to understand the recharge process along the foothill region as well as riparian zone.

Abstract

Quality of water is affected by natural and man induced contamination to groundwater system. Area chosen for study has gained its own importance due to the location of two lignite mines and a Thermal power plant in operation. Extensive large scale pumping of water is done for lignite mining. The mine drainage and drainage from thermal power plant along with agricultural return flow from lignite charged waters increases the severity of problem. In order to achieve a panacea for the above-mentioned situation, the study has incorporated and integrated in all related factors to get a meaningful interpretation for groundwater quality and quantity management in and around Neyveli area. The frequent failure of monsoon has added to the existing problem of over exploitation. To attain a panacea for water chemistry groundwater samples were collected for four different seasons. Higher EC and TDS values are observed in Southeast and Southwest part of the study area. In Southwest monsoon and Summer seasons HCO₃Cl dominates the anions, with few representations for SO₄. In Northeast monsoon and Post monsoon season Na + K – Ca + Mg is the dominant. Thermodynamic, studies reveal that groundwater of the region are stable with Kaolinite stability field in all the silicate systems. Bicarbonates derived from silicate mineral weathering are noted in the NW, Northern and in the mining region. These regions are located in the NW and NE part of the study area. Comparison of water quality to standards shows that the water can be used for drinking and for irrigation purposes except in few locations.

Abstract

Radon being the radioactive daughter product of Uranium; the interrelationship between U and Rn has been established in the present study. It is found that Radon coexist with Uranium in the region. A total of 61 samples were collected spatially from hand pumps and bore wells of the study area. Major ions such as Ca²⁺, Mg²⁺, Na⁺, K⁺, F^-, Cl^-, HCO^3-, NO^3-, H₄SiO₄,PO₄- and SO₄^2- and U, Rn were analysed. The lithological influence of U and Radon occurrence is also highlighted. Hard rocks especially Granites are the source for both U and Rn in the study area whereas the lack of correlation exist between U and Rn in sedimentary terrain can be attributed to difference in flow conditions and chemical properties of these elements. 

Key words: Radon, Uranium, Granite, Ground water, Source.
 

11.1 Introduction

The laws governing the flow of water in wells are referred to as the hydraulics of wells. Just like surface water flows from a higher elevation to a lower elevation by gravity, groundwater also flows from a region of higher water table to a region of lower water table. This difference of water table measured by any two piezometers divided by the longitudinal distance between them is called as hydraulic gradient. Hydraulic gradient plays a dominant role in deciding the flow of groundwater. This hydraulic gradient together with the hydraulic conductivity of the aquifer material forms the main law of well hydraulics called as Darcy’s law. An understanding of Darcy’s law together with some other laws as discussed subsequently in this chapter is essential in order to know the discharge of a well in a particular formation. Darcy’s law is valid for studying groundwater flow in alluvial formations. However, it is not valid for aquifers having hard rock areas.

10.1 Introduction

During rain or heavy irrigation, a part of the rainfall or irrigated water moves below the effective root zone of the crop which moves further below and adds to the water table lying above the impermeable bed or hard rock which is called as  ground  water  reservoir. At  times  the  accumulated  surface  water  is  also recharged to the soil reservoir both naturally as well as artificially that add to the underlying ground water reservoir. This groundwater is an important source of water for irrigation as well as domestic uses. It is the most abundant fresh water resource of the earth. Underground water reservoirs contain large stock of fresh water resources. Total quantity of groundwater within 800 m distance below  the  ground  surface  is  more than  30  times  the  total  water  in  all fresh water lakes, more than 60 times the total water in soil and other unsaturated rock materials, more than 300 times the water vapour in the atmosphere and 3000 times the average volume of all rivers and rivulets in the world (Lenka, 2001). But the distribution of groundwater is not uniform.

9.1 Introduction

Flood water which is in the form of a hydrograph when passes down a river section undergoes several changes in its form. There may be some addition of water to the river section when the flood wave passes down the river section. There may be some diversion of water from the section. Thus, depending on the addition or abstraction of water to the incoming flood water, shape of the flood hydrograph in the downstream section may change. Sometimes channel storage and resistance to flow of water in the channel section also affects the shape of the flood hydrograph.

8.1 Introduction

The knowledge of statistics and probability is very helpful for correct prediction of hydrological data and correct prediction of hydrological data is useful in giving good performance in all water resources projects. Since hydrological data are highly stochastic varying both in space and time, it is essential to predict them as correct as possible. The hydrologic evens do not depend on physical and chemical laws but depend entirely on nature. They cannot be predicted exactly by using any relationship but can be predicted at different probability levels by fitting suitable probability distribution functions. Application of statistics and probability in the field of hydrology can help to predict the hydrologic events in a better way. In hydrology, objectives of statistics are as follows (Suresh, 2008):

7.1 Introduction

Flood is an unusually high stage in a river resulted due to high rainfall or snow melt which causes large flow of runoff in it. During flood, the river overflows the banks and inundates the adjoining areas. Flood causes heavy damages to buildings and hydraulic structures besides causing catastrophic loss to human life and property. It causes great economic loss due to disruption of many structures and damage to agricultural fields. Many forest and aquatic lives are affected by the flood. Hundreds of crores of rupees are spent every year to control, forecast and manage the flood.

6.1 Introduction

When rainfall strikes a ground surface, some losses like initial and infiltration will occur. After these losses are fulfilled, runoff will begin. The runoff will ultimately reach a stream. The main routes through which runoff flows are (i) overland flow, (ii) interflow and (iii) groundwater flow. Overland flow which is also called as surface flow flows over the land mass and reaches a stream. Overland flow soon reaches a stream and if it occurs in sufficient quantity, it forms an important element in the formation of flood peaks. In small and moderate storms, there may have predominant initial and infiltration losses resulting minimum amount of surface runoff and this is especially true in case of permeable soils. If the soil is impermeable, then there may have reasonable runoff. However, surface runoff is an important factor in streamflow only for heavy or high intensity rainfall.

5.1 Introduction

A steam can be defined as a flow channel in to which the surface runoff flowing over the land surfaces and base flow/ground flow flowing below the ground surfaces meet. It receives the total flow from a specified basin. Streamflow representing the runoff phase of the hydrologic cycle is the most important basic data for hydrologic studies. Interestingly, stream flow is the only part of the hydrologic cycle that can be measured accurately. Stream flow is a historical data and like rainfall and runoff, it is a stochastic hydrologic variable. It is also called as discharge or rate of flow. Discharge is defined as the volume of water flowing through a cross section in a unit time.

4.1 Introduction

Precipitation is a major component of hydrological cycle. It occurs because of condensation of water vapour molecules in the atmosphere. When the precipitation falls on the grounds, it undergoes several phases before it appears as runoff in the streams. Certain amount of precipitations is intercepted by the foliage of plants and roofs and other parts of the building and other hydraulic structures. This intercepted water is called as interception loss which is evaporated to the atmosphere. Sometimes the dried surface of the buildings and other structures soak certain amount of precipitation while falling on them which also adds to interception loss. After striking the land masses, certain amount of the precipitated water gets infiltrated into the soil surface which then moves both in lateral as well as in vertical direction. This loss is called as infiltration loss. For the study of groundwater, infiltration loss is not a loss but rather it is a gain in terms of groundwater recharge. However for a surface water hydrologist, it is a loss since it decreases the amount of runoff contributing to the stream or any other water bodies.

3.1 Runoff

Runoff is one of the important parameter of hydrologic cycle. It is defined as that portion of precipitation which is not absorbed by the deep soil strata but finds its way into the stream after meeting the demands of evapotranspiration, interception, infiltration, surface storage, and surface as well as channel detention. It includes surface runoff received into the channels after precipitation occurs, delayed runoff that enters the stream after passing through the land surface, and other delayed runoff from the temporarily detained pits, depressions, swamps or detained as snow fall. It is thus the flow collected from the drainage basin and appearing at the outlet of the basin. The runoff process is demonstrated in Fig. 3.1 as flow chart. Details of the runoff process are discussed as below.

2.1 Introduction

Precipitation is the general term for all forms of moisture emanating from clouds and then ultimately falling on the land surface. It is the total supply of water derived from the atmosphere in the forms of rain, snow, hail, mist, dew, sleet, fog etc. The liquid form of precipitation is called as rainfall whereas the frozen forms of precipitations are snow, hail and sleet. Of all the different forms of precipitation, rain and snow are the two dominant factors that contribute maximum amount of water. In Indian condition, rainfall is the most important form of precipitation that contributes the highest amount of water causing stream flow. Unless otherwise stated, the term rainfall will be used in this book synonymously with precipitation. It is the primary input vector of the hydrologic cycle. Generally it is expressed as the depth water on a horizontal surface over any specified time interval. If the specified time interval is day, then the amount of precipitation is called as daily precipitation. Similarly, the precipitation being contributed over time interval of a month, season and year is termed as monthly, seasonal or annual precipitation. Its form and quantity are influenced by the action of different climatic factors such as wind, temperature and atmospheric pressure. The study of precipitation forms a major portion of the subject of the hydrometeorology.

1.1 Water and its Importance

Water has played a crucial role in sustainace of lives of all living beings including animals, plants and human beings in this earth since time immemorial. It is there since the creation of the nature and will probably remain till the destruction of the nature. It is used in multifarious uses including domestic, industrial, agricultural, recreational and many other uses. It occurs in the nature in practically three forms i.e. solid, liquid and gaseous forms. All the three forms are important to living beings; but the liquid form of water is more beneficial. The weight of the water helps in running hydroelectric turbines, the density of water helps in floating the ships, the steam energy produced by heating the water helps to run the locomotives and thus is beneficial in many ways. It is considered as the most important resource of the society. It has become part and partial in our life so that we cannot live without water. That is why water is called as life.

Vegetation is a key component in hydrologic modeling. Transpiration, a component in hydrologic cycle, is contributed by vegetation. Most of the hydrologic model thus includes vegetation as a parameter. For accurate and appropriate model output, first requirement is good quality data. Most of the time, the data on vegetation is confusing, as in literature various researcher have used different values for common vegetation parameters. Here some common parameters of some important crops, which yield good quality results, are given.

Kharif crops are generally sown during last week of May and first week of June, while rabi crop are sown during last week of November and first week of December. But this period will vary from region to region as well as depends on variety of crop.