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Journal of Environmental Quality 30:356-368 (2001)
© 2001 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America

ARTICLE
ENVIRONMENTAL ISSUES

Effect on Water Resources from Upstream Water Diversion in the Ganges Basin

Miah M. Adel

Interdisciplinary Sciences Research Center, Dep. of Chemistry and Physics, P.O. Box 4941, Univ. of Arkansas at Pine Bluff, Pine Bluff, AR 71611

Corresponding author (miah_m{at}vx4500.uapb.edu)

Received for publication September 30, 1999.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
Bangladesh faces at least 30 upstream water diversion constructions of which Farakka Barrage is the major one. The effects of Farakka Barrage on water resources, socioeconomy, and culture have been investigated downstream in the basins of the Ganges and its distributaries. A diversion of up to 60% of the Ganges water over 25 yr has caused (i) reduction of water in surface water resources, (ii) increased dependence on ground water, (iii) destruction of the breeding and raising grounds for 109 species of Gangetic fishes and other aquatic species and amphibians, (iv) increased malnutrition, (v) deficiency in soil organic matter content, (vi) change in the agricultural practices, (vii) eradication of inland navigable routes, (viii) outbreak of water-borne diseases, (ix) loss of professions, and (x) obstruction to religious observances and pastimes. Further, arsenopyrites buried in the prebarrage water table have come in contact with air and formed water-soluble compounds of arsenic. Inadequate recharging of ground water hinders the natural cleansing of arsenic, and threatens about 75000000 lives who are likely to use water contaminated with up to 2 mg/L of arsenic. Furthermore, the depletion of surface water resources has caused environmental heating and cooling effects. Apart from these effects, sudden releases of water by the barrage during the flood season cause devestating floods. In consideration of such a heavy toll for the areas downstream, strict international rules have to be laid down to preserve the riparian ecosystems.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
REPORTS are available on the relative merits and demerits of using dams and barrages on rivers to divert and block water for irrigation and production of hydropower (Paranjpye, 1988; Gillis, 1992; Water Power and Dam Construction, 1995; Kwai-cheong, 1995; Chau, 1995; The World Bank Group, 1996; Schuking, 1999; The Times of India Online, 2000). However, few reports are available for downstream riparian countries. Bangladesh faces at least 30 dams, barrages, and other water diversion facilities upsteram on various major rivers. Figure 1 illustrates them along with major rivers and dams in West Bengal, India (Abbas, personal communication, 1992; Joint River Commission, Dhaka, Bangladesh, personal communication, 1996; Sattar, 1996, p. 55–57; India Drainage, Calcutta, personal communication, 1996).



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  		Fig. 1. Illustration of the common rivers of India and Bangladesh. The rivers having water diversion construction upon them are identified with small circles around them (Abbas, personal communication, 1992; Joint River Commission, Dhaka, Bangladesh, personal communication, 1996; Sattar, 1996, p. 55–57; India Drainage, Calcutta, personal communication, 1996)

 
This study reports a partial picture of the destructive effects in a delta region of water blockage, upstream diversion, and sudden water releases.


   PROJECT SITE
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
Parts of the basins of the Ganges and its Baral and Musa Khan distributaries (Fig. 2) were selected for the study. Farakka Barrage over the Ganges is a major diversion and the only one where the extent of water diversion is known. Farakka Barrage lies over the Ganges about 18 km upstream of the Indo–Bangladesh border. A test run of the Barrage started in 1975. The purpose was to flush the Hugli river, which had siltation due to construction. In 1975, with the change of the ruling party in Bangladesh, the test run of the Barrage turned into a permanent diversion by the neighboring country.



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  		Fig. 2. Illustration of the project site showing courses of the Ganges and the Baral and Musa Khan distributaries

 
The surface water resources have been degraded during the last 25 years. As to the pre-dam era sizes and distribution of the affected surface water resources in the project site, about 1 km of a distributary course would have had, on the average, three canals of width 3 m and depth 2 m. The average size of ponds would have been 30 x 20 x 5 m and that of ditches 20 x 10 x 2.5 m. The ratio of the average sizes of ponds, ditches, and canals would have been about 20:10:1. However, a floodplain typically would have been a few hundred to a few thousand times larger than a pond. Surface water reservoirs would have accumulated monsoon and Ganges water, resulting in ground water recharge. Variations in river flows would have remained within 5 to 25% from year to year, and for nearly 6 mo of continuous flows in the rivers, water accumulation in floodplains, canals, and ditches would not have worked as sinks to reduce the flow in the distributaries.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 
To find the effect of upstream water diversion on the downstream delta, a data-based study of the adverse effects on the salient features of the deltaic life was made in the project site, which included the districts of Naogaon, Nawanganj, Rajshahi, and Natore, the basins of the main river Ganges, and the distributaries of the Baral and the Musa Khan (Fig. 2). The prominent features covered were the Ganges discharge; the deltaic surface water resources, such as the distributaries, floodplains, ponds, ditches, and canals; the quality of drinking water; agribusiness; socioeconomy; culture; and climate. The Ganges flow data were obtained from the Water Development Authority, Dhaka, Bangladesh. Field surveys were made to acquire data for areas, water levels, and water-holding times of 175 floodplains, 100 ponds, and 100 ditches; and to acquire data for the loss of fish resources, sources for domestic water supply, agricultural practices, the loss of professions, and obstruction to religious observances and pastimes in 100 villages. The climate data for the project site were obtained from the Meteorology Office, Dhaka, Bangladesh. These pieces of information were obtained for both the pre- and post-dam periods for comparison of the environmental scenarios pertaining to the two periods.

The average depths of these surface water bodies were determined by the following relation:

[1]
where ai is the area and di is the corresponding depth for diffent fractions of surface water bodies. Different areas of specific surface water reservoirs—floodplains and ponds—having the same depth were cumulatively added to get the information on average depths and areas. Other than the Ganges annual flow, pre-dam and post-dam times refer to the periods of 1968–1981 and 1982–1995, respectively.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 CONCLUSION
 REFERENCES
 
Discharges in the Ganges
The mean monthly flows in the Ganges, illustrated in Fig. 3 , show the effect of water withdrawal. The top three curves refer to the Farakka point (Schwarz et al., 1993) and the bottom two to the Hardinge Bridge point, located about 174 km downstream from the common border, a stretch of watercourse without a water diversion project. Because of the government ban on the water diversion data, it is not possible to show the same year's data at both points. UNESCO (1979, p. 57), however, provides a comparison of the flows for 1973 (Fig. 4) . The flow at the Hardinge Bridge point had been about 1.4 times higher than that at the Farakka point. The gradual decrease of water in the Ganges at the Hardinge Bridge point is illustrated in Fig. 5 (Hebblethwaite, 1997). A few peaks in Fig. 5 after 1975 resulted from short-term water-sharing treaties between longer-term unilateral withdrawals. The pre- and the post-1975 mean discharges had been 1932 ± 22.8 and 769.5 ± 284.5 m3/s, respectively. Hillary (1979)(p. 35) reports of the post-dam period that during the dry season, almost all the water of the Ganges is withdrawn by India. The resulting condition of the Ganges in 1993 is shown in Fig. 6 . The fissured ground lets air into the ground, and reflects, absorbs, and radiates solar radiation, instead of the almost complete absorption when it had been covered with water.



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  		Fig. 3. Illustration of the monthly average flow rate of the Ganges for the years 1850, 1900, and 1980 at the Farakka point, and for 1963 and 1993 at the Hardinge Bridge point

 


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  		Fig. 4. A comparison of the pre-Farakka discharges in the Ganges recorded at the Farakka point in India and Hardinge Bridge point in Bangladesh

 


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  		Fig. 5. Illustration of the average annual discharge rate of the Ganges through the Bangladesh delta (Hebblethwaite, 1997)

 


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  		Fig. 6. A picture of the fissured Ganges bed (courtesy of Shakoor Majiid). Latent heat sources have been turned into sensible heat sources

 
Ganges Distributaries
The Mahananda is the only tributary of the Ganges in Bangladesh. The main distributaries of the Ganges in Bangladesh are the Baral, the Gorai, the Arial Khan, the Bhairab, the Mathabhanga, the Kumar, and the Ichamati. Distributaries have daughter distributaries. The daughter distributaries are the Musa Khan, the Madhumati, the Pashur, and the Kabodack. The Baral flows about 80 km before it joins with the Atrai to fall into the Brahmaputra. The Baral used to discharge, on the average, at least 2000 m3/s for at least 5 mo (July–November) annually. Now, it can hardly discharge one-fourth of that amount. A shoal of about 1 x 1/2 km has formed in its mouth. The weak flushing power in the Ganges, and consequently in the Baral, has favored the formation of the shoal over the years. The pre-dam perennial surface water source has been about 50% perennial and 50% seasonal in the post-dam era.

The daughter distributary of the Baral is the Musa Khan, which is about 20 km long. It used to discharge annually at least 1000 m3/s during July through November. A shoal of about 100 x 10 m has obliterated its point of origin from the Baral. All the aquatics and the amphibians that lived in a stretch of about 20000 x 12 x 2 m of watercourse during November through June and in about 20000 x 100 x 10 m during July through November, along with sportive Gangetic dolphins, are gone. The river can no longer feed thousands of ponds, ditches, and more than 900 km2 of floodplains. An estimated hydrograph for the live Musa Khan for 1963 is illustrated in Fig. 7 .



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  		Fig. 7. A hydrograph for the Musa Khan for 1963

 
Floodplains
Figure 8 illustrates the cumulative areas of floodplains versus the monsoon-season (mid-August to mid-September) average water depths for pre- and post-dam periods. Floodplains that used to have water for 12 mo within depths of 1.1 to 2.2 m, 10 to 11 mo within depths of 0.70 to 1.10 m, and 8 mo within depths of 0.25 to 0.60 m, can now have water for 6 mo, 4 mo, and 1 to 3 mo, respectively, making an overall spatial and temporal drop of about 50% and a drop in ground water recharging.




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  		Fig. 8. a. A comparison of the monsoon season water depths for ponds in pre- and post-dam days.

b. A comparison of the dry season water depths for ponds in pre- and post-dam days

 
Ponds
Pond water depths have been plotted against the corresponding areas in Fig. 8a,b. The monsoon season water depth in the post-diversion era is about the same level as the dry season water depth in the pre-diversion era. The water contents of the second-largest surface water resource have been reduced by about 50% making also a decrease in ground water recharge.

Ditches
Ditches would provide seasonal jute retting, fish raising, and cleaning water facilities. They would hold water from July through February, depending on their depths and locations. Additionally, bushy sides of ditches had been abodes of migratory birds, which are no longer observed. These dry reservoirs have been absorbed into agricultural land or homesteads.

Use of Water Sources
Currently, 38% of rural families are dependent on ground water year-round and a 36% are dependent for 6 mo, whereas almost 100% of the families would depend on surface water for almost 100% of time annually during the pre-dam era. Also, currently, almost 100% of the urban population depends on ground water annually, whereas 30 to 50% of the families would depend on surface water for almost year-round in the pre-dam era.

Surface water quality has deteriorated in the post-dam era. Patches of stagnant water in rivers, ponds, and floodplains contain large amounts of suspended matter and and algae (2.00–5.00 g/L) for most of the time.

Depletion of Natural Fish Breeding Grounds
The surface water resources had been the breeding and raising grounds of 109 species of Gangetic fishes (Islam and Hassan, 1983). For about 10 mo annually (July–April), people would fish the surface water resources to supplement their income and dietary intakes (Hughes et al., 1994). A few ponds have deep or shallow tubewells set in them to extract ground water for fish raising. The pre-dam annual catch of some of the popular species is given in Table 1, and the source-wise annual catch is given in Table 2 for the Musa Khan basin. The dashes in Table 1 indicate that the species are extinct in the basin. The breeding of these fishes would take place April through August. Hilsha, the most popular species, has a second breeding time in January through March. In the pre-dam era, the question of overfishing would not arise because of maintenance of balance in the dietary intake of fish along with meat, varieties of beans, and vegetables by the Bangladeshis, and the control of fish catch by the owners of privately owned fish-raising water bodies (ponds) with the decline of the fishing season.


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  		Table 1. Species-wise annual fish catch (kg) in a rural unit in the Musa Khan Basin. Species names appear in italics below the local names

 

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  		Table 2. Source-wise monthly fish catch (kg) in pre-Farakka and post-Farakka in a rural unit in the Musa Khan Basin

 
Fish had been the cheapest source of animal protein (6.25%), one of the indispensibles of life, and calcium (25%) (Ahmed and Hassan, 1986). The total population of the project area had been about 5 million in 1975. Today's projected population is about 10.5 million. In 1981–1982, when the project areawide population had been 5.6 million (Miah and Samad, 1996), it was found that diets of 76 and 97% of the households did not meet the calcium and protein requirements, respectively (Ahmed and Hassan, 1986). Currently, the project area population has doubled and the cheapest sources for protein and calcium have been depleted.

Further, decomposed bodies of frogs, snails, turtles, reptiles, and disliked species of fish would add about 1 kg of organic matter annually to every 100 km2 of seasonally inundated soil. Many of these species are currently extinct. Furthermore, the Ganges water would bring oxygen, nitrogen, lime, and phosphorus for brisk growth of rice plants in the pre-dam era (Ganguli, 1938, p. 38).

Changes in Agricultural Practices
A change in agricultural practices for jute (Corchorus olitorius L., C. capsularis L.) sugarcane (Saccharum officinarum, S. spontanaeum), and rice (Oryza sativa L.) has been found. Whereas jute takes about 3 mo to grow, sugarcane takes four to five times as long. Farmers would earn cash during July through September by selling jute. Also, they would earn cash in mid-November through March by selling sugarcane. Live floodplains and ditches served as the facilities for retting of jute. The current climatic irregularity, however, is not favorable for jute growth. Jute lands are being used for rice and sugarcane cultivation. The jute products—ropes, bags, sacks, mats, and artificial wood partex (out of jute sticks)—are a renewable resource, and jute fields would be self-manured from the dead and decomposed leaves of the plant. The balance between the cultivation of jute and sugarcane is lost, as illustrated in Fig. 9 by plotting an index defined to be the percent of land used for a specific crop for 1970–1995 in the area surveyed. Jute sticks would be widely used for cooking fuels for about 6 mo annually, and per head of domestic livestock about 1 kg of rope would be used annually.



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  		Fig. 9. A change in the agricultural practices. The index along the y axis represents the percent of cultivated land used for a specific crop

 
Aeration and Reaeration of Water
The lack of running water over the basins has caused a deficiency of dissolved oxygen in recharging water. Fast-moving shallow streams that would keep the basins inundated at least during July through October had more aeration than sluggish deep streams or stagnant ponds or floodplains (O'Connor and Dibbins, 1958).

The basins of the Musa Khan and the Baral have lost the stream currents in distributaries, canals, floodplains, ponds, and ditches by almost 100% both in temporal and spatial scales.

Loss of Inland Navigable Routes
People would come from distant places like Barisal to do business in biweekly market places located at intervals of about 5 km by the side of the Musa Khan and the Baral. These market places had been inland river ports where thousands of tons of goods would be transported twice a week. While those market places have expanded because of population pressure, with the drying and the dwindling conditions of distributaries, goods are transported via roads and highways causing at least 5% fatalities/wk/km trip on crowded roads and highways. Distributaries provided cheap inland transportation routes, reducing costly and accident-prone land transportation. Generations-old trees were cut down to widen roads and highways to complement transportation. This destroyed habitats and was a forced deforestation in an underforested (<10%) country.

Hygienic Effects
People living by the Musa Khan river never realized the need of digging ponds to have privately owned water bodies. Fishermen residing on the Musa Khan bank lived in boats for 9 mo annually. These fishermen's wives reported to the author in December of 1994 of having no water to bathe in during the summer. The country's news media reported of finding skin diseases like scabies, leprosy, yaws, trachoma, and conjuctivitis due to bathing in unclean surface water. Also, Schwarz et al. (1993) reported that principal infectious diseases related to water supply are typhoid, paratyphoid, fever, bacillary dysentery, amoebic dysentery, diarrhea, cholera, hepatitis, poliomyelitis, stomach disorder, schistosomiasis, drocontiasis, guinea worm, roundworm, and hookworm. However, no statistics for the project site have yet been prepared for these indirect effects of water shortage following Schwarz et al.'s (1993) report.

Loss of Professions
Apart from farming, the people in the basins were employed as fishmen, pottermen, boatmakers, fishing equipment makers, fishing technologists, and providers of transportation by hackney carriages. It was found by survey that the number of these professionals dropped from 6, 4, 0.4, 5.4, 4.3, and 0.9% to 0.5, 0.5, 0.08, 1.3, 1.2, and 0.1% of the rural population, respectively. Only the number of rickshaw pullers increased, from 1.3% to 5.9%. As to the lost typical fishing assets, a population of 150 fishermen would make 350 fishing nets of 20 kinds for catching 15 to 20 varieties of fishes. These cottage industries and the technical hands in the basins have become extinct.

Obstruction to Religious Observances and Pastimes
In the pre-dam era, the Hindu minority group living in the basin of the Musa Khan would plunge their statues of the gods and goddesses (Dugra, Kali, Swaraswati, etc.) in water during October through January. Since the death of this distributary, these Hindus cannot observe these festivals in pomp and grandeur locally.

Further, during the pre-dam period, surface water resources would turn into natural facilities for swimming, angling, boat racing, etc. These pastimes are gone from the Musa Khan basin.

Ground Water
The U.S. Geological Survey reports surface water and ground water as a single resource (Winter et al., 1998). Filling of surface water resources and the recharging of ground water would occur during June through October. During November through May, evaportranspiration would drop the ground water table about 4 m (with 50% soil porosity; the actual water depth is 2 m) below the wet-season level, as would be found, during the dry season, from water levels in ponds and open wells, and by digging of new ponds and open wells. Every year the ground water is sinking by at least 0.5 m (Department of Public Health Engineering, Rajshahi, Bangladesh, personal communication, 1995). Although the drop in water table varies from place to place, a comparison of the depths of recently and pre-dam installed tubewells suggests about a 10-m drop in water table.

Arsenic Contamination of Ground Water
The USEPA recommended concentration limit of arsenic in drinking water is 0.05 mg/L (Masters, 1991, p. 205), and the arsenic concentration in ground water is 40 times as high. It is thought that depleting ground water has let air get in the ground below the pre-dam water table. Arsenopyrites buried in this layer of sediment formed water-soluble compounds of arsenic, which infiltrated to water. Although iron can purify water of arsenic in the presence of oxygen, this self-purification of ground water has not occurred completely since the water diversion started because of inadequate recharging water carrying scanty oxygen into the ground water. The self-purification reactions (Braman, 1983) are as follows:

[2]

[3]

[4]

The precipitated ferric arsenate later undergoes other transformations.

Arsenic investigators (Nickson et al., 1998; Bearak, 1998) have ignored the water diversion issue, although it has hindered water's self-cleansing of arsenic for lack of oxygen. This process is observed in Lake Michigan (Seydel, 1972) because of a fresh oxygen-rich supply of water every year. Also, Meng and his coworker (Stevens Institute of Technology, Hoboken, NJ) have patented a technique based on the self-cleansing reactions to purify the arsenic-contaminated water in Bangladesh and Mexico (Meng, personal communication, 2000).

The rehabilitation of arsenic patients in the society poses a potential problem for the government.

Climatic Changes and Health Effects
An analysis of the climate data reveals that the summertime pre-dam maximum temperature has risen from 37 to 43°C and the wintertime minimum temperature has dropped from 8 to 4°C in the post-dam era (Adel, 2000). Further, the frequency of the highest relative humidity in post-dam period is 1.6 times higher than that in pre-dam period. The frequency of >100 mm rain events has been halved, causing a proportionately reduced infiltration from the monsoon rainfall, because the likely recharge occurs when (i) the soil has a high conductivity, (ii) the watertable lies at shallow depth, (iii) the soil is relatively wet, and (iv) the water input rate is low and lasts for a relatively long time interval (Freeze, 1969).

Reports are available on the appearances of health effects such as hypertension, asthmatic conditions, and increased patient suffering due to temperature fluctuations (Kalkstein and Valimont, 1987, p. 122–152; Hussain and Hays, 1993; Rogot and Padgett, 1976). It was found that one in every four families has an asthma patient, and more than 10% of the families have three asthma patients. Also, most of the asthma patients above 50 yr of age suffer from diabetes, hypertension, and stroke, the latter being the number one crippler and killer disease. Further, a general kind of aridity prevails in the city of Rajshahi, favoring uplift of aerosol dusts in the air. From the daily intake of 20 m3 of air, an adult individual inhales about 10 mg of dust. Annually, an adult individual inhales 2 g of dust (Adel, 1999). The inhalation of dusty air triggers allergic reactions in asthma patients and patients having asthma-like symptoms.

Increased Occurrences of the Worst Floods
Bangladesh has become more flood-prone than it was in the pre-dam era. Floods have hit unprecedentedly in the southwest, northwest, northern, eastern, and central parts of the country in the post-dam era from time to time. Dams are used as flood outlets during the flood season when the upstream country cannot withhold the rising flood water. Floods cause irreparable damage to crops, livestock, and above all, humans. The project site becomes the first affected area when the Farakka barrage is opened to get rid of the excess water. Bangladesh is never given a warning of potential floods by the neighboring country, forcing it to face the flood without preparation (Miah, 1997). The flood of 2000 inundated areas in Rajshahi, Nawabganj, Kustia, Satkhira, and Jessore (Abdullah, 2000; News from Bangladesh, 2000). In Rajshahi, dead bodies were seen floating in the Ganges. Many people from the neighboring Indian downstream districts took shelter in the northwestern and southwestern parts of Bangladesh. It is reported that Bangladesh border forces had to guard against the upstream country's border forces' action of water release through Bangladesh (News from Bangladesh, 2000). The country had to appeal for international help to cope with the flood situation. The assessment of the damages cannot be made until the flood water recedes.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
CONCLUSION
 REFERENCES
 
Water Resources
In the pre-diversion era, the water balance (surface water and ground water together) in the basin area would be given by

[5]
where P (about 1.5 m/yr) stands for precipitation, STRMin (about 0.5 m/yr) for inflow to the basin via rivers and canals, GWin for subsurface inflow from ground water movement, GWout for subsurface outflow from ground water movement, and E (about 2 m/yr) for evapotranspiration. The quantities in Eq. [5] represent their long-term average values. Currently, STRMin = 0 and GWin and GWout depend on the elevation of the watershed and hydraulic conductivity. The hydraulic conductivity is uniform in the region under consideration. The approximation of GWin = GWout can be justified by Darcy's law for the flow rate (G) as the product of transmissivity, boundary width, and average of the initial and final hydraulic conductivities at the boundaries divided by the area of the region (Van Tonder and Kirchner, 1990). A typical value of lateral flow may be taken as 6.25 x 10-2 m/h (Strahler and Strahler, 1973). The current form of Eq. [5] is an inequality given by

[6]

Currently, the temperature rise has caused an increased potential evapotranspiration, making E > 2 m/yr, and indicates depletion of the water resources.

Arsenic Contamination
The fraction of the contamination from the production site, namely, arsenopyrites, that reaches the ground water table at a depth L within certain time period t, annually, can be shown to be (Sauty, 1980):

[7]
where Cwo, Co, vx, t, and DL are the concentration (g/m3) of arsenic reaching water surface, the initial concentration (g/m3) at the production site, the average infiltration velocity (m/d), the time (d) since release at the source site, and the longitudinal hydrodynamic dispersion coefficient (m), respectively. For DL = 9.05 x 10-10 m2/s (Freeze and Cherry, 1979; Neuman, 1990; Vanysek, 1992), t = 120 d (July through October, the recharging time), L = 10 m from the contaminant source site to ground water table, vx = 5.56 x 10-10 m/s (calculated from the weighted average of soil types and the infiltration rate in them), and = 0.78.

The current concentration of arsenic is thought to be a cumulative effect during 25 years since 1975. Focusing on the dissolved amount, the growth of the contamination over one year in an aquifer of the size of a district can be written as:

[8]
where C, A, R, E, and i stand for the dissolved arsenic (g), the area of a district (m2), the recharge (m/yr), the evapotranspiration (m/yr), and any year in the post-dam era, respectively. The first factor in Eq. [8] yields the increase in the dissolved amount for inadequate recharging and oxygen shortage. The second factor is unitless and gives the increase in concentration due to evapotranspiration. Subramanian and Kosnett's (1998) observation supports the second factor. Average district size in Bangladesh is A = 2.16 x 109 m2. For a thickness X meters of an unconfined aquifer at the end of summer with Ri - Ri+1 = 0.5 m (annual recharging shortfall), Ri+1 = X + 4 m (thickness after recharge), Ri+1 - Ei+1 = X m (thickness at the end of the summer season), and C = 1.44 x 109 Cwo/yr = 1.12 x 109 Co/yr. The determination of Cwo must come from a survey throughout the district and on-site observation of arsenic release. Although no time series of the development of the contamination has been maintained, the district of Nawabgang showed the first arsenic victim in 1990. Afterward, arsenic patients were found in Jhenaidah when Sylhet and Chittagong had been free from arsenic. As time went on, these regions were also found to be contaminated in increasing amounts before the end of the century. The district-wise contaminant levels are illustrated in Fig. 10 (Bearak, 1998).



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  		Fig. 10. Illustration of the arsenic-contaminated districts in Bangladesh and West Bengal along with the rivers having upstream water diversion projects (Abbas, personal communication, 1992; Joint River Commission, Dhaka, Bangladesh, personal communication, 1996; Sattar, 1996, p. 55–57; India Drainage, Calcutta, personal communication, 1996; Bearak, 1998; Subramanian and Kosnett, 1998)

 
The entrance of oxygen to the ground has increased due to the sinking of the ground water table and an increase of the width of the unsaturated zone, causing interaction of oxygen with arsenopyrites in the ground found by Das et al. (1996) and Karim et al. (1997). In pre-dam periods, water in soil pores would block the flow of air. The higher concentration of arsenic at the upper part of aquifers is a consequence of water use and inadequate replenishment at the top of aquifers.

The arsenic contamination of ground water has risked about 75000000 lives in 64 districts shown in Fig. 10. The number is computed from the users of ground water from contaminated tubewells in affected areas. Also, the figure shows the arsenic contamination of ground water in West Bengal without the inter-district boundaries. Bangladesh has not undergone any biogeophysicochemical changes other than the shotage of surface water over the last 25 years.

Climate Change
The temperature fluctuations found cannot be related to global warming, although there has been a global temperature rise in the 1980s in low-latitude regions (23.6° N to 23.6° S). Hansen and Lebedeff (1988) found a temperature rise of about 0.6, 0.7, and 0.75°C for 1980, 1983, and 1987, respectively, due to global warming in that decade. On the contrary, the temperature fluctuations in the project site showed a monotonous increase during 1981–1985 (Adel, 2000) and has been showing a monotonous decrease during the wintertime since 1981.

Climatic changes are in keeping with the observations Revelle and Waggoner (1983), Bouwman (1990), and Rind (1995). The increase in temperature is due to the conversion of the latent heat sources to sensible heat sources, which has increased surface albedo and emission. Because of the high specific heat of water, water bodies could gain heat in summer and withhold it for emission to the environment during the winter. These heat reservoirs are gone with the surface water reservoirs. The increase in the frequencies of high relative humidities is due to the rise of temperature, which enhances potential evaporation. Although the moisture from the ocean predominates, the effect of evapotranspiration on the land cannot be ignored as a source of rain water.

Increased Flood Frequency
The increased occurrences of devastating floods is related to the siltation of river beds in the wake of dam and barrage construction that weakens river flow. Prakash (1998) reports of a sediment deposition of more than 20 m at the Farakka Barrage point in 22 years (1975–1997). A proportionate amount of sediment has accumulated elsewhere in the Ganges and its distributaries. The decrease in river depths is too much too accommodate the flood water, which has not dropped at all from its magnitude in the pre-diversion era. Inundation of wide areas is needed to accommodate the excess water. On top of this, monsoon rainfall worsens the situation.


   CONCLUSION
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
REFERENCES
 
Shortage of water in a downstream country puts both lives and life styles at stake. About a 60% water diversion by Farakka Barrage caused a 50% drop in the surface water availability and a proportionate drop in the recharging ground water. Natural wetland ecosystems have been depleted, causing a destruction in breeding and raising grounds of the Gangetic fishes and an increased malnutrition among the people. The water shortage has affected generations-old rural professions and farming practices. It has affected transportation, religious observances, pastimes, and water sports. Also, the situation has deprived the annual addition of organic matter to the soil. Further, water-borne diseases have increased. In absence of streams, aeration and reaeration to scanty surface water have been reduced, and with the shortage of recharging water, oxygen addition to ground water has been inadequate to perform its natural cleansing of arsenic. Furthermore, changes of latent heat reservoirs to sensible heat reservoirs have caused a microlevel change in the climate along with the outbreak of climate-related diseases. Additionally, dams are used as flood outlets by the upstream country without any prior warning signals. These lessons demonstrate the importance of protecting riparian ecosystems.


   ACKNOWLEDGMENTS
 
The author is thankful to the workers, particularly M.A. Samad of Bangladshi-American Experimental Mission, for conducting surveys in the Ganges basin. Thanks are also due to the Agargaon Climate Office, Dhaka, Bangladesh, for supplying the rainfall data. Further thanks go to individuals who have supplied illustrations used in the article.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 PROJECT SITE
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES
 





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