ENVIRONMENTAL IMPACTS OF IRRIGATION AND CLIMATE SMART AGRICULTURE
Muhammad Nazim1, Haseeba Maryam2 and Qurat-Ul-Ain Sadiq3
1*Department of Agronomy, Muhammad Nawaz Shareef, University of Agriculture Multan, 66000 Pakistan
2 Institute of Soil and Environmental Science, University of Agriculture Faisalabad,38000 Pakistan.
3Department of Soil and Environmental Sciences, Muhammad Nawaz Shareef, University of Agriculture Multan, 66000Pakistan.
Pakistan is one of the most climate susceptible countries in the world. Climate change has become global issue for crops due to increase in temperature, less rainfall resulting in shortage of water and decrease in crop yield. On the global level, climate change has become an issue of severe and immediate concern having far-reaching effects not only on agricultural productivity but also on the demand for water and energy.
During the past century, global temperatures have risen by nearly 1°C (due to burning of hydrocarbons and deforestation) and are expected to increase further by 1.4 to 5.8°C by the year 2100. In the past few years, the climatic condition got worsened and signs of global warming have become evident.
With climate change and elevation of average temperatures, there are increased risks of rising sea levels, melting of glaciers, flooding and higher frequency of droughts. Consequently, crop yields are expected to decrease, affecting livelihoods and food production.
The water availability per capita is lower than enough volume, per capita water availability at the time of independence was 5,600 m3 in comparison with current measurements which are 1,000 m3 and the this shortage is expected to rise about 31% according to needs of population by 2025. In current scenario of climate change and water shortage, Irrigated lands has greater contribution to the world agriculture output and food supply.
Estimations collected in 1986 indicated that about half of the increase in agricultural productivity in the previous 35 years had come from irrigated land, about one-third of the world’s crops were grown on the one-sixth of the cropped area which was irrigated, and the irrigated land was, on average, more than twice as productive as rain-fed land. Although water on earth is abundant, but 97% of the world’s water lies in the ocean and seas, 2% of all water is in glacial ice, and only 1% of all water is available for human use.
The environmental impacts of irrigation are related to the changes in quantity and quality of soil and water as a result of irrigation and the effects on natural and social conditions in river basins and downstream of an irrigation scheme. The impacts stem from the altered hydrological conditions caused by the installation and operation of the irrigation scheme.
Environmental Impacts of Irrigation
An irrigation scheme draws water from groundwater, rivers, lakes or overland flow, and distributes it over an area. Direct effects include reduction in downstream river flow, increased evaporation in the irrigated area, increased level in the water table as groundwater recharge in the area is increased and flow increased in the irrigated area. Similarly, irrigation has adverse impacts on the moisture content of the atmosphere.
Increases or decreases in irrigation are a key area of concern in precipitation shed studies, that examine how significant modifications to the delivery of evaporation to the atmosphere can alter downwind rainfall. Indirect effects are those that have consequences that take longer to develop and may also be longer-lasting. The indirect effects of irrigation include Water logging, Soil salination , Ecological damage and Socio-economic impacts.
The indirect effects of water logging and soil salination occur directly on the land which is being irrigated. The ecological and socioeconomic consequences take longer to happen but can be more influential. As a result, the overall water level decreases. This may cause water mining, soil subsidence, and, along the coast, saltwater intrusion. The reduced downstream river flow may cause disappearance of ecologically and economically important wetlands or flood forests.
These reduced availability of industrial, municipal, household, and drinking water. These also altered shipping routes and reduced fishing opportunities, The Indus River in Pakistan faces water scarcity due to over-extraction of water for agriculture. In village and agri.
Land waterlogging and drainage problems are mostly negative consequences. Reduction in agricultural productivity can be caused due to increased level of water table. If water table are shallow then applications of irrigation reduced which produces leaching and soil salinity problems .To overcome the adverse effects caused by shallow water tables and salinization, some kinds of salinity, water logging and drainage system is needed.
Due to drainage of surface and groundwater in the project area, waters salinized and polluted by agricultural chemicals like biopesticides and polluted river water entering the sea may adversely affect the ecology of the sea. The natural build up of sedimentation can reduce downstream river flows due to the installation of irrigation systems. The benefits of heavy deposits of sedimentation can be seen in large rivers like the Nile River.
In Baluchistan due to new irrigation developments Water becomes scarce for nomadic pastoralist. Downstream water users often have no legal water rights and may become victims of the development of irrigation. Flood-recession cropping may adversely affected by the upstream interception of river water for irrigation purposes. In Baluchistan province of Pakistan, the development of new small-scale irrigation projects depleting the water resources of nomadic tribes traveling annually between Baluchistan and Gujarat India.
After the diminishing the Kainji dam, Nigeria, 50 to 70 per cent of the downstream area of flood-recession cropping was lost. Irrigation projects may reduce the fishing opportunities of the original population and the grazing opportunities for cattle. Due to the livestock pressure on the remaining lands, overgrazing may increase which cause soil erosion and the loss of natural resources.
The depletion of groundwater aquifers, which is caused by the suppression of the seasonal flood cycle, is damaging the forests downstream of the dam. When more groundwater is pumped from wells than water becomes replenished, storage of water in the aquifers is being mined and the use of that water is no longer sustainable. Eventually it may become so difficult to extract groundwater that farmers may be forced to abandon irrigated agriculture. Some examples include:
- In Baluchistan, Pakistan, the development of tube well irrigation projects was at the expense of the traditional qanator karez users.
- Groundwater-related subsidenceof the land due to mining of groundwater occurred in the United States at a rate of 1m for each 13m that the water table was lowered.
The effects of irrigation on water table, soil salinity and salinity of drainage and groundwater, and the effects of mitigative measures can be simulated and predicted using agro-hydro-salinity models. In the Indus Plains in Pakistan, more than 2 million hectares of land is waterlogged. The soil of 13.6 million hectares within the Gross Command Area was surveyed, which revealed that 3.1 million hectares (23%) was saline. 23% of this was in Sindh and 13% in the Punjab.
The Asian Development Bank (ADB) states that 38% of the irrigated area is now waterlogged and 14% of the surface is too saline for use. In India 2.19 million ha have been reported to suffer from waterlogging in irrigation canal commands. Also 3.47 million ha were reported to be seriously salt affected.
The downstream drainage water quality may deteriorate owing to leaching of salts, nutrients, herbicides and pesticides with high salinity and alkalinity. There is threat of soils converting into saline or alkali soils. This may negatively affect the health of the population. For example, The Aral Sea, is seriously polluted by drainage water.
Irrigation can have a variety of negative impacts on ecology and socioeconomy, which may be mitigated in a number of ways. These include siting the irrigation projects in an area where negative impacts can be minimized. The use of sprinkler irrigation and micro-irrigation systems decreases the risk of waterlogging and erosion. Where practicable, using treated wastewater makes more water available to other users. Maintaining flood flows downstream of the dams can ensure that an adequate area is flooded each year.
It often takes time to accurately predict the impact that new irrigation schemes will have on the ecology and socio-economy of a region. When that is the case, the project managers will often only change the project if the impact would be originally expected. Frequently irrigation schemes are seen as extremely necessary for socioeconomic well-being especially in developing countries.
In order to help alleviate and prevent major environmental impacts, they would use techniques that minimize the potential negative impacts. The main purposes of the irrigation project were to reduce poverty, improve food security, develop local employment, increase household income and enhance the sustainability of land use. Due to this careful planning this project was successful both in improving the social-economic conditions in the region and ensuring that land and water are sustainability into the future.
Despite a general decline in fertility rates, world population is still growing rapidly. It is projected that world population will reach between 7.5 and then 10.5 billion by 2050, depending on future growth rate scenarios. The population in the LAC (Latin America and the Caribbean) region should almost reach 700 million people by 2025 from 475 million in 1997. The world population is expanding rapidly, with corresponding increased pressures on the food supply, environment and water.
Competition for water is becoming critical, and environmental degradation related to water usage is serious. The number of people living in water-stressed countries is projected to climb from 500 million to three billion by 2025. Agriculture is the major user of freshwater, with a world’s average of 71% of the water use. The large and growing proportion of the population living in urban areas will put considerable pressure for continued transfers of water out of agriculture to supply growing urban centers.
- Introduce water and power pricing that better represent the market value of water.
- Introduce transferable water entitlements.
- Set limits for allowable groundwater recharge (amount and quality) and introduce penalties for exceeding these limits.
- Provide incentives for land reclamation.
- Require exhaustive environmental impact assessment for new irrigation projects.
- Incorporate environmental impact considerations in the design, construction, and operation of new irrigation projects.
- Improve maintenance of irrigation infrastructure.
- Construct drainage facilities.
- Reduce canal seepage, i.e.Through lining.
System management interventions:
- Improve the operation of existing irrigation and drainage infrastructure through management information systems.
- Increase farmers’ involvement in management and maintenance of irrigation and drainage facilities.
- Evaluate the feasibility of implementing on-demand water delivery to farms.
Irrigation/agronomic practices interventions:
- Minimize water losses in the on-farm distribution system.
- Improve irrigation systems performance to minimize deep percolation and surface runoff.
- Improvement watercourse and precision land leveling.
- Instead of surface irrigation drip irrigation is installed.
- Introduce different crop rotations.
The potential to increase substantially of the irrigated areas of the world is limited. Gains from new capacity are expected to be largely offset by losses such as waterlogging and salinization, as well as retirement of areas being irrigated by pumping water in excess of rates of recharge. On the other hand, managing existing irrigation projects so as to minimize their environmental impact is a requirement for long-term sustainability of irrigated agriculture.
One area of concern is that developing countries could spend the next 50 years struggling to provide safe drinking water and sanitation to their exploding urban populations and enough irrigation water to maintain the high levels of food production. The unresolved global warming issue could turn to be the major challenge for water development during the next 50 years, or it may not be. Prudent decision-making requires consideration of potential climate change scenarios on long-term decisions regarding water use and environmental impact.
M.Sc.(Hons.) Crop Physiology, Department of Agronomy, MNS-University of Agriculture, Multan, Pakistan.