ACCORDING to Section 12 of the Pakistan Environmental Protection Act, 1997, no proponent of a project shall commerce construction or operation, unless he 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.
The EPA will review the IEE or the EIA and then according its approval. The review of the EIA will have to be carried out with public participation. According to a follow-up of the Pakistan Environmental Protection Agency review of the IEE and the EIA regulations, 2002, the irrigation and drainage projects, serving less than 15,000 hectares will require submission of the IEE and, all irrigation and drainage projects, serving 15,000 hectares and above, will require submission of an EIA.
Indus river: The Indus plain covers an area of about 202,000 square kilometres (sq km) and the Indus basin irrigation network commands about 14.60 million hectares. The Indus river has the 12th largest drainage area in the world and 7th largest delta.
The current mean flows in Indus river is 190 billion cubic metres (cu m)/year (154 million acre-feet-MAF/year). Of this, about 130 billion cu m/year (105 MAF/year) is used for irrigation. while, 49 billion cu m/year (39 MAF/year) releases below Kotri barrage. In effect, the releases below Kotri barrage are much lower due to the system losses, evaporation, increased upstream water abstraction and, the existence of water storage reservoirs i upstream reaches. A major impact of low discharges below impact of low discharges below Kotri barrage would be an increase in the level of nitrates and pesticides in groundwater. The presence of nitrates above the World Health Organization’s guideline value of 10mg /1 (milligrams / litre), in drinking-water, would cause methaemoglobinaema (blue-baby syndrome) condition in infants.
There are 14 irrigation systems in Sindh, which cumulatively receive water from 3 barrages across the Indus river. Under the National Drainage Programme (NDP), projects of various magnitudes are being executed. Construction of new and rehabilitation of existing drains is part of the work envisaged under the NDP. The left bank Outfall Drain (LBOD) caters for effluent drainage from the areas on, left bank of the Indus River, while the Right Bank Outfall Drain (RBOD) is being taken in hand at an estimated cost of Rs14 billion. Two projects are proposed during the execution of the RBOD, one, construction of long, deep-sea outfall and a caution not to discharge an 14.70 million cubic metros per day affluent as this disrupts the marine ecosystem. To minimize marine pollution and prevent ecological consequences, it is prudent to discharge saline effluents deep into the sea. And, instead of wasting saline effluent into the sea, it can be desalinated by using solar energy. Assessment: To minimize environmental consequences, it is wise to forecast, assess, determine and evaluate environmental trends at different levels. The EIA enables development of the project, use of water and land in a sensible way and helps avoid irreversible environmental damage. The EIA has three basic functions; (a) predict problems, (b) devise strategy to mitigate adverse impacts and enhance positive effects; and (c) to formulate an environmental action plan to deal with the impact on a long-term basis. This also includes an environmental audit of the project, after it is completed. The process starts with screening and scooping. Impact: The project’s impact on environment and external factors should be taken into consideration. Construction of upstream reservoirs reduces the availability at downstream, intensification of agriculture leads to groundwater pollution and the improved efficiency again reduces flows, posing problem for irrigation and wildlife habitat. During the construction phase, localized resources go under stress due to the population influx. Insanitation and diseases problems rise, as external population is not immune to local vectors of disease. Variations in river regime, during low flows have negative impact. This can best be explained by the example of Kotri barrage. Decades back, despite low flows sufficient water for dilution was present which checked the level of pollution. Sea intrusion was not a problem, mangroves were flourishing, there was no drinking water problem for downstream users (including Karachi), no irrigation of crop was affected.
Now, during the low flows in the Indus river (November-February), there is little water flowing beyond the Kotri barrage and, this impacts drinking, fishing, recreation, irrigation, mangroves, river purification, etc. The low salinity-tolerant species of mangroves have been wiped out. Rivers support rich habitats along their sides. Variations in flows adversely affect the species. In addition, increased salinity breeds anopheline vectors of malaria, as they feed on waters with high salinity.
While, lowering of water table seems attractive on its face value, it also has some consequences. It is noted that over a period of 50 years in Central Valley, California, a 60-metre drop in groundwater level led to a 3-metre drop in ground level. Land subsidence, with associated damage to structures, including the hydraulic structures, is a serious negative impact. Lowering the water table will be beneficial for agriculture. It also affects those who are dependent on groundwater for their domestic use. In case the users are poor, they will have to seek alternate source for water source for water supply, which may be contaminated and would be an economic burden on them. Hence, changes in water table need to be assessed in economic terms. Lowering of ground level would favour the sandfly, which is a vector for diseases like visceral leihmaniasis. Assimilative capacity of stream (ability to absorb pollution) is affected by the drainage projects. Change in the hydrological regime would alter the assimilative capacity.
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. It is not easy to treat pesticide-laden waters. Besides, they are persistent and biomagnify in the food chain, as they move from tropic level to next higher tropic level. Pesticides like the 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. Phosphates tend to be fixed to soil particles. They each streams only, where soil is disintegrated. Pollution of water bodies by agrochemicals is a serious problem in the Sindh province. In slow-moving surface water bodies and, especially in lakes, the excessive use of nutrients causes eutrophication (weed growth).
Increase of hydrogen ion concentration coupled with the presence of ammonia is toxic to fish life. Use of excrete as fertilizer is one source of ammonia. Also, use of excrete as fertilisers, especially when it is not fully stabilized, will transport pathogens to water bodies causing widespread health complications due to the presence of bacteria, virus, protozoa and helminths. Organic pollution, including excrete, provides an ideal breeding ground for culicine mosquitoes which transmit filariasis.
Salinization is an adverse impact of irrigation projects. According to the FAO, arable land is continuously going out of production at the rate of about 5 to 7 million hectares per year, due to soil degradation. Irrigation projects affect soil properties adversely. Soil structure is damaged by its accumulation. Structure may collapse due to sodium ion.
People move into the project area from other places in search of livelihood. Livestock also moves in resulting in the use of forest and trees for fuel wood. Vegetative cover also decreases due to grazing, resulting in soil erosion, which in turn, leads to the siltation problems and exposure of area to floods.
Transport of soil particles by wind or water not only causes sedimentation of reservoirs but also clog 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, do not absorb rainfall and consequently, the runoff is higher. The runoff may cause erosion of the land which comes in its path.
Change in water-use and land-use impacts the ecology, aquatic ecosystems, natural habitat, biological diversity of species and the individual groups (bids, fish, insects). Endangered species is most at risk. Nesting sites are intruded. Land value increases which may cause deforestation and ecological imbalance. More important is the issue of wetlands. The provide buffer to floods, act as a system for water purification and protects coast from erosion. The are a highly productive ecosystems and support a vide variety of life. Estuaries, mangroves and tidal wetlands are 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.
Women’s role is likely to be affected in the changed land pattern as irrigation activities quite often bring male folks to the fore. Women’s role is relegated to the agriculture aspect.
Health impact: 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 their banks. In addition, pending 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.
Environmental health engineers must monitor the health status during the project construction and during its initial months of operation in line with the environmental action plan.
ACCORDING to Section 12 of the Pakistan Environmental Protection Act, 1997, no proponent of a project shall commerce construction or operation, unless he 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.
