Abstract: The Indus river Dolphin is one of the world`s most endanger cetaceans with a total population of just a few hundreds individuals. Ecological interest in the species was aroused in the 1970`s and inter mittend but largely un- coordinated monitoring of a number as continued never since. Barrages cutting the river in to biologically up stream combine with the pressure associated with a growing population in a Third World country pollution such as fragmentation and literacy combine to put the species under threat. The establishment of a dolphin Reserve between the Guddu and Sukkur barrages in Sindh has made a positive contribution to dolphin conservation but a more proper approach is advocated here. Accepting that little can be done to improve the natural impacts, approaches reducing the pollution load of the river water, particularly in low flows, by natural filtration are advocated.
INTRODUCTION
The Indus River represents one of the major water distribution systems of south East Asia and is the most important river of Pakistan Ittekkot and Arain, 1986. In Pakistan, like other countries of the world, the level of pollution of fresh water bodies, the especially the rivers, is often no longer within safe limits for human consumption. Water is said to be universal solvent because most of the biochemical reactions take place in it, thus making it essential for all forms of life (Ahmed et al., 1989). Surface water is a visible natural resource and is intensively used for various purposes in all countries of the world. The major sources of surface water contamination are municipal and industrial discharges and agricultural run off. The direct and indirect effects of fishing and pollution, both domestic and industrial, have reduced the population to a few hundred individuals in the central section of the main Indus River (Gachal and Slater, 2003). Surface water pollution is one of the major problems particularly in developing countries. In many countries, the treated water from lakes and other sources is being used for drinking and various other purposes. If polluted water is not properly treated, it gives rise to serious health problems for human beings, animals and aquatic life (Gachal and Slater , 2002; Khan and Khan, 1980) The food resources may very along the river. Pollution from agriculture, industrial chemical and human waste which might have physiological effects on dolphins or their prey or in extreme cases might prove fatal (Gachal and Slater, 2004).
The Indus River is an important source of livelihood of millions of people. It mainly supplies water for drinking purposes to towns and agriculture side along its entire route (Tahir et al., 1990). The Indus River system naturally supports a great variety of flora and fauna. Pilleri (1972) described the water quality of the river as good for human consumption as well as the animal life in the Indus River. (Leen et al., 1990) and Dudgeon (1992) showed concern for the water quality of Asian Rivers. Else where Rozengurt (1993) quoted the decline of the Sardine catch due to the ecological degradation of the Nile River in Egypt.
The World Conservation Union regards this species as vulnerable (Klinowska, 1991; Reeves and Leatherwood, 1994; Smith et al., 1994) said the species is threatened by rapid deterioration of the habitat due to pollution, construction of dams, mining and directed and incidental catch.
However, the present study is aimed at evaluating the pollution status of the river through physico-chemical analyses dolphin population. Further, Indus river water, sewage and industrial effluents were collected for analysis from Rohri, Sukkur, Guddu locations in the Sindh provinces of Pakistan. It is also a part of this project to explore the ecology of Indus dolphin, which is endemic to the Indus river system to determine the effect of seasonal variations on some physico-chemical parameters of the river ecosystem.
MATERIALS AND METHODS
Water samples were collected every month for a period of nine-months (April to November 1999) from midstream at the depth of 100 cm from 13 to 14 locations between Sukkur, Rohri and Guddu according to standard water sampling procedure (Table 1).
Water samples were collected in polyethylene litre screw cap containers, which were cleaned sequentially with detergent wash, tap water rinse, 24 h soak in 1% HNO3 and several distilled water rinses, then dried, capped and labeled. Each container was filled to the brim with river water and effluents to avoid any space. The samples were transported to the laboratory as quickly as possible and various water quality physico-chemical parameters were determined by standard methods. Physico-chemical parameters like pH, conductivity, temperature (air and water), total dissolved solids, alkalinity, hardness, residue (total, volatile, fixed), Dissolved Oxygen (DO), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) were subsequently evaluated in laboratory.
Temperature (air and water) was measured with a mercury thermometer, visibility by (Secchi disc), using a WTW 320 conductivity bridge for conductivity, salinity and TDS, Orion 420A pH meter was used for pH determination.
Dissolved Oxygen by Winkler method, hardness, chloride and alkalinity by titrimetry or by titration with standard EDTA, silver nitrate and hydrochloric acid respectively, residues (total, fixed and volatile) by gravimetry, COD by dichromate reflux oxidation method.
Biological oxygen demand was evaluated by Winkler method (samples were placed in temperature-controlled incubator at 20°C for five days (model cooled orbital incubator 0-70°C GallanKamp).
RESULTS
Water samples collected from Indus River sites were analyzed in the laboratory for physico-chemical parameters.
pH: pH values have been observed at Sukkur, Rohri and Guddu from the months of March to September, 1999, but suddenly decreased from the month of May to September due to higher dissolution of salts in the river water when river was at its highest flow. Observed pH range of Indus River water is 6.5 to 8.13 (Table 1-4). The permissible pH limit recommended by WHO for drinking, irrigation waters and fish population is 6.5-8.5.
Conductivity: Conductance values of water samples are indicative of presence of electrolyte concentrations and are greatest during low flow of the Indus River. Sample 13 had highest conductivity 5650 μS cm–1 in September and lowest 205 μS cm–1 in sample 12 in July 99 (Table 1-5). However, fluctuation observed in the samples is due to water flow in the river. The standard for electrical conductivity is 400 μS cm–1, as the water quality depends on TDS. However, WHO standard for TDS ranges between 500-1500 ppm.
Alkalinity: The lowest and highest values of alkalinity of Indus river were observed in March and August, respectively and ranged between 25-113 mg L–1 (s-1, S-9, Table 1 and 5), respectively. However, fluctuation observed in alkalinity values (Table 2-4 and 6) indicate the presence of variable amounts of carbonates, bicarbonates, borate, hydroxide in the Indus river. Acceptable alkalinity values ranges between 30-500 mg L–1.
Hardness: The values of hardness ranged from 208 mgL–1 in August to a minimum of 42.66 mg L–1 in September (Table 4 and 7). The permissible limit for hardness is 100 mg L–1 for drinking water as recommended by WHO.
Total Dissolved Solids (TDS): The amount of total dissolved solids was found to be 3616 mg L–1 (S-13) in September, 99 and 131 mg L–1 (S-14) in the month of June, 99 (Table 4 and 7). Total dissolved solids values showed a fluctuating trend at all locations throughout the period of study. Maximum of 400 mg L–1 of TDS is permissible for diverse fish population. But, our findings at different location of Indus river water are potentially threat to aquatic life particularly fish growth.
Chloride: The lowest and highest values of chloride contents were observed in September 782 and 32.61 mg L–1 in May 99 respectively (S-14, S-13, Table 2 and 7). Fluctuation in chloride contents was noted at different locations during the study period. However, WHO recommended the permissible limit of 250 mg L–1 for drinking water.
Chemical Oxygen Demand (COD): Chemical Oxygen Demand (COD) of the river water samples were determined. The lowest and highest values of COD ranged between 10 to 400 mg L–1 in the months of September and July 99 respectively (Table 5 and 7). High values showed the presence of organic pollutants in the river water samples, which are susceptible to oxidation. High COD values are a threat to river life.
| Table 1: | Physico-chemical analysis of Indus River water March 1999 |
BOD: Biological Oxygen Demand, COD: Chemical Oxygen Demand,
TDS: Total Dissolve Solids, S: Sample = S1, Rohri, S2 Rohri mix, S3 Mid
River, S4 Bunder road, S5 Thermal Sukkur, S6 Mirani mosque, S7 Sadbelo (pumping
station), S8 Sukkur Regent, S9 Purano Sukkur, S10 Makrani paro, S11 Begari,
S12 Guddu Thermal, S13 Guddu channel 1, S14 Guddu channel 2. A: Absent:
o: Out of range |
|
| Table 2: | Physico-chemical analysis of Indus River water April |
| Table 3: | Physico-chemical analysis of Indus River water May 1999 |
| Table 4: | Physico-chemical analysis of Indus River water June 1999 |
| Table 5: | Physico-chemical analysis of Indus River water July 1999 |
| Table 6: | Physico-chemical analysis of Indus River water August 1999 |
A COD value 0.5 mg L–1 indicates very clean stream. The permissible level recommended by World Health Organization ranges 10-15 mg L–1.
Biological Oxygen Demand (BOD): Biological oxygen demand level was determined during the study period from March 99 to September. Values of BOD reflecting organic pollution was highest in low flow conditions but within the range 2.74-4.61 mg L–1 in April to September 1999 (Table 1- 5).
Dissolved Oxygen (DO): The lowest and highest values of dissolved oxygen were evaluated (Table 2 and 7).
| Table 7: | Physico-chemical analysis of Indus River water September 1999 |
Whereas, minimum and maximum value ranges allowed by WHO lies 4-7 mg L–1 dissolved oxygen for drinking water and fishes, respectively.
Total, fixed and volatile residue: The river and its tributaries receive effluent discharges as they pass near the villages and towns. Indus River water is used for agricultural purposes in lower Sindh. Arain and Khuhawar (1982) examined the transport of carbon and minerals from Kotri to Arabian Sea.
Total residue values were estimated from March to September but within the range 250-3600 mg L–1, in the months of August, September and May 99 (Table 3, 6 and 7). The volatile residue varied between 100-2000 mg L–1 (Table 4 and 7). Fixed residue in water samples ranged 40-1200 mg L–1 (Table 3, 4 and 7). Indus River carried a lot of silt and suspended solids, which pushes high total residue and fixed residue (Dewani et al., 1997; Ittekkot et al., 1986) also reported similar observations below Kotri barrage.
Tariq et al. (1996) described the Indus River as a dump house for all types of waste products streaming into river via its tributaries. The Government of Pakistan says the occurrence of massive fish kills and the destruction of lower aquatic forms due to indiscriminate use of pesticides in the agricultural fields along Indus River banks and are due to the release of industrial pollutants into water bodies.
Pilleri (1972) described the river water quality as good aquatic habitat. Since the species gained legal protection and international status and regular monitoring took place. Leen et al. (1990) and Dudgeon (1992) have showed the concern for the water quality of Asian Rivers. Rozengurt (1993) quoted the decline of the sardine catch due to ecological degradation of Nile River in Egypt.
Chaudhry et al. (1999) reported 7% annual rise in the use of fertilizer and 190% increase in the imports of pesticides between 1981 and 1987. The indiscriminate use of agricultural chemical leads to chemical pollution of the environment and may kill all animal life including fish and bioaccumulate through the food chain leading to dolphin contamination (Gachal and Slater, 2002).
DISCUSSION
The Indus River represents one of the major water distribution systems of south East Asia and most important river of Pakistan Ittekkot and Arain 1986. The Indus River, in Pakistan is one of the world’s largest rivers in terms of drainage basin area (970,000 km), discharge and sediment load. The loss of fresh water inputs and release of industrial and domestic waste are probably the most serious ecological threats. Indus River carried lot of silt and suspended solids, which pushes high total residue and fixed residue (Dewani et al., 1997). Voltile residue represented the organic matter presented in the total residue. Ittekkot et al. (1986) also reported similar observations below Kotri barrage. Arain and Khuhawar (1982) examined the transport of carbon and minerals from Kotri to Arabian Sea. The Indus river has a maximum amount of total residue 3600 mg L–1 in September 1999.
Jaleel et al. (1991) voiced concern about the deteriorating state of fresh water with respect to metal pollution. Chaudhry et al. (1999) showed that pollution on River Ravi a tributary of the Indus has caused a drop in fish production of 5,000 tones per year, a consequence of pollution, which will be reflected throughout the food chain.
Total Dissolved Solids (TDS) in Indus River (S-13) had a maximum range 3616 mg L–1 in September 1999 and Chemical Oxygen Demand (COD) has high value 400 mg L–1 in July 1999. Where as hardness has the maximum of 208 mg L–1 in August 1999 due to high values of TDS. Biological oxygen demand (BOD) has the elevated value reflecting the organic pollution in flow conditions of the River as the large quantities of feacal material floating on the River surface was noted in December 1999 (Table 7).
However, unregulated sewage, industrial effluent and agricultural run off find their way into the Indus River at various places. Consequently, the Indus River acts as a dump house for all types of waste products streaming into it (Tariq et al., 1996). This all leads to high oxygen demand and depletion of oxygen level in the water body with harmful effects on aquatic life.
The River Indus and its tributaries suffer considerable pollution, some continuous as in the case of sewage and other sources. The increasing need for freshwater for industrial and domestic use is the main reason for the dolphins endangered status (Gachal and Slater, 2004). It is probable that a more wide-ranging approach to dolphin conservation might be of more value. If the pollution load of the river can be reduced then it would benefit both human and wildlife dependent upon river. A solution to the pollution problem needs to be relatively low cost. Wherever there is human habitation and/or industry along the river there is a generally untreated foul water discharge into the waterway. In many parts of the world, particularly in Europe and North America polluted waters are treated by passing them through natural or constructed wetlands (Perttu, 1993).
In a number of areas along the Indus, particularly in upper Sindh, sewage or industrial discharges could be diverted away from the river into underutilized areas peripheral to the river. Depending on the volume and pollution load of the effluent, the water could be allowed to rejoin the main river at varying distances from the input point having passed through this peripheral treatment area. The treatment area should be initially planted with wetland plants, particularly woody species and these allowed to develop and where possible to be harvested successionally as fuel. Such a filter system would reduce the BOD, COD as well as bacterial and chemical pollutants to an environmentally acceptable level (Gachal and Slater, 2002). The area would also have value as a fuel resource and as a wetland for wildlife. This holistic approach of cleaning the environment to the benefit of all river users could have a positive effect upon dolphin population by controlling pollution in the food chain.