April 30, 2007	Monday	Rabi-us-Sani 12, 1428

ACCORDING to the Section 12 of the Pakistan Environmental Protection Act, 1997, no proponent of a project shall commence construction or operation, unless the proponent has filed with the Environmental Protection Agency (EPA), an initial environmental examination (IEE), or where the project is likely to cause an adverse environmental effect, an environmental impact assessment (EIA) and, has obtained from the EPA approval of the project.

According to the follow-up the Pakistan Environmental Protection Agency Review of IEE and EIA Regulations, 2000, the irrigation and drainage projects, serving less than 15,000 hectares, require submission of an IEE and, all irrigation and drainage projects, serving 15,000 hectares and above, require submission of an EIA.

Impacts of drainage projects: While evaluating drainage projects, two scenarios must be taken into consideration. One is the impact of the project on the environment and, the second is the externalities (external factors on the project). Environmental impacts of drainage projects are numerous. Construction of storage reservoirs upstream will reduce the availability of water downstream. This specifically applies in case of Sindh province. Intensification of agriculture generally leads to groundwater pollution. Improved efficiency, again, may lead to reduced downstream flows, which could be a problem in some irrigation schemes, or wildlife habitats, which are dependent on downstream flows.

Various stages of the implementation of the project will vary the impacts. For example, during construction, localised resources go under stress, due to population influx. Insanitation and disease problems will arise, as external population is not immune to local vectors of diseases. Variations in river regime, during low flows can have significant negative impacts. This can best be explained by example of the Kotri barrage.

Decades back, despite low flows, there used to be sufficient water for dilution. This checked the level of pollutants. Sea intrusion was then not a problem, because of sufficient discharge of water. Mangroves were flourishing, as plenty of water was available. There was no drinking-water problem for downstream users (including Karachi), as enough water used to flow. No irrigation of crops was affected due to water availability.

Now, during low flows in Indus River (November-February), there is little water flowing beyond the Kotri barrage and, this has impacted all sectors (drinking, fishing, recreation, irrigation, mangroves, river purification, etc). The low salinity-tolerant species of mangroves have been wiped out. Another adverse impact, that is often overlooked, is that, when the pollutants get concentrated, due to low dilution, the water quality gets poorer. Downstream water treatment plants, which abstract water for treatment, face a major financial problem. The water treatment costs become exorbitant, when the raw water quality is poor. That is why, water engineers always insist that, the water catchments area should be kept pollution-free.

Rivers supports rich habitats along its sides. Large variation in low flows would adversely affect the species’ diversity. Estuaries ecology is sensitive to increased levels of salinity. In addition to the affect on estuarine environment, the increased salinity will breed anopheline vectors of malaria, as they feed on waters with high salinity (more than 5,000 pp – parts per million).

Lowering of ground level would favour sandfly, which is a vector for diseases like visceral leihmaniasis. A newspaper reports the outbreak of leihmaniasis in Dadu and Larkana districts due to the same reason. According to a report by Food and Agricultural Organisation (FAO), particular care is needed in drainage of coastal swamp regions, as ferrous sulphate soils can become severely acidic, resulting in the formation of “cat-clays” (FAO, 1995).

Assimilative capacity of stream (ability to absorb pollution) is affected by the drainage projects. Change in the hydrological regime would alter the assimilative capacity. Low flows tend to reduce the ability of stream to get rid of pollutants. High flows allow those pollutants that attach themselves to particles, to be carried away from the system. Dissolved salts become problems, as their concentration increase high enough to be toxic during low flows.

Stream water quality is adversely affected by the irrigation and drainage projects. Pesticides are closely associated with such projects. They are discharged into the streams, causing water pollution problems. It is not easy to treat pesticide-laden waters. Besides, they are persistent and bio-magnify in the food chain, as they move from one tropic level to next higher tropic level. Pesticides like DDT and dieldrin, in particular, are highly hazardous to aquatic life.

Fertilisers are also closely associated with irrigation and drainage projects. Nitrates are highly soluble and, therefore reach streams quickly. Health effects of nitrates are discussed elsewhere above. Phosphates tend to be fixed to soil particles. They reach stream only, where soil is disintegrated. Pollution of water bodies by agrochemicals is a serious problem in Sindh province.

In tropical developing countries, since ambient temperatures are relatively high, the solubility of oxygen in stream is low. Low dissolved oxygen in water is further exacerbated by the algal growth. This will cause suffocation of fish and other aquatic biota and, depending upon the flows and degree of turbulence, may cause anaerobic conditions in receiving stream. Onset of anaerobic conditions will lead to odour problems, due to the generation of hydrogen sulphide gas, besides release of global warming gases.

Increase in the pH value, coupled with the presence of ammonia, is toxic to fish life. Use of excreta as fertiliser is one source of ammonia. Also, use of excreta as fertilisers, especially when the excreta is not fully stabilised, will transport pathogens to water bodies, causing widespread health complications, due to the presence of bacteria, virus, protozoa and helminthis. Organic pollution, including excreta, provides an ideal breeding ground for culicine mosquitoes, which transmit filariasis.

Salinity is a major adverse impact of irrigation projects. According to FAO, arable land is continuously going out of production at the rate of about five to seven million hectares per year, due to soil degradation (FAO, 1992). Saline conditions affect crop yield and limits the output potential of soil. Proper irrigation practices, including adjusting crop patterns and, changing tillage techniques, are required to minimise the salinity problems.

Irrigation projects affect soil properties adversely. Soil structure is damaged by salts’ accumulation. Soil structure collapse may occur due to the increased availability of sodium ion. While, use of gypsum as soil amendment, would help reduce the sodium content, this would mean incurring an additional investment. The problem of soil acidification exists in case of acid sulphate soil. Low pH would decrease the ability of plants to take up nutrients. A major impact of decreased pH is the mobilisation of heavy metals in the soil and, their subsequent uptake by the fruit crops.

Saline drainage is the outcome of drainage projects. Reducing salt inputs is one way of reducing salinity of the drain water. Solute concentration always increases from applied irrigation water to drain water. Typically, salt concentrations in drainage water are two to ten times higher than in irrigation water. Leaching helps in washing away the salts, but this add extra 10 per cent of water in the system. The best course is to use good irrigation practices.

Population influx is a potential impact of irrigation project. Due to the irrigation or drainage project, people move into the project area from other places, in search of livelihood. Livestock, which is associated with such populations, also move in. This results in the use of forest and trees, for fuel wood. Vegetative cover is also decreased, due to grazing, resulting in soil erosion, which in turn, leads to the formation of silt and, exposure of area to potential threat from floods.

Transport of soil particles, by wind or water, not only causes sedimentation of reservoirs (silt formation, as noted above), but also clogs water abstraction points downstream. A common observation is the malfunction of pumping stations. Increased sediment load may change the river morphology and, this would affect the river ecology. Local erosion may also occur, as the irrigation land, being comparatively wetter, does not absorb rainfall and, consequently, the runoff is higher. The runoff may cause erosion of the land, which comes in its path.

Irrigation and drainage projects impact the river morphology. In a steady state river, the sediments are carried by the flow of water and, no sediments are deposited, change in the river flows, both low and high, occur due to drainage. In case river flow lowers, the reduced flow velocity allows sediments to settle out and, the sediments transport capacity is reduced. This changes the size of wetted perimeter of the river of the river. Estuaries, mangroves and tidal wetlands are an important nursery of offshore fish. Reduction of freshwater would alter salinity levels. High salinity levels will result in stunted growth of mangroves and, will wipe out salt-sensitive species. Riverine irrigation, an important part of irrigation system in Sindh, also depends on overflows from Indus river. Irrigation projects can have direct impact on wetland by changing hydrological conditions.

Health Impact: By far, the major impact of irrigation and drainage projects is on human and animal health. These projects create ideal breeding grounds for vectors of diseases. Canals and drainage structures usually have weed growth on the banks. In addition, pounding of water also occurs. Depressions are created which are filled with seepage. Poor drainage allows breeding of mosquitoes and, hence the transmission of mosquito-borne infections.