Sustainability of Irrigated Agriculture in Pakistan

Irrigated agriculture has been practiced in the Indus Basin since long, however canal irrigation network along with diversion structures were mainly constructed in the second half of nineteenth and first half of the twentieth century. At present Indus Basin Irrigation System consist of 3 storage reservoirs, 19 barrages, 43 main canals and 12 inter river link canals. The total length of the canal system is more than 60,000 km and over 100,000 canal outlets supply water in cultivated areas. The system was initially designed for low cultivation intensities (average 63% for Punjab), which increased to almost double (120%) due to excessive demand in food and fiber to meet the needs of growing population.

Sustainable development requires that needs of present should be met without compromising on future developments. Sustainability of irrigated agriculture can broadly be grouped into economic, social and environmental sustainability.

Economic Sustainability:

Besides food self-sufficiency, achieving net profit over the long term is the motivating factor that sustains irrigated agriculture. Economically acceptable irrigation systems provide lifestyle and social options for farmers and also contribute to the wider economy and community. To maintain and improve economic acceptability in irrigated agriculture, larger investments are some times required to enhance water availability and increase water use efficiency. The long-term economic sustainability demands that development and management cost need to be assessed and incorporated in the economic analysis to work out the benefit cost ratio.  When the marginal benefit is less than the marginal cost, the irrigation practice loses its economic acceptability, which implies an unsustainable state.

Social Sustainability:

Irrigated agriculture has deep social impacts.  Any change in the policy, management, distribution can cause serious problems. The system should be designed in such a way that it causes least negative social impacts even in the worst scenarios.  The equitable distribution of available resources is the most important thing in this context. The conflicts arise frequently among the people if they are not convinced or properly informed about the system. In countries like Pakistan, where people have generally low temperament, the system need to be designed in such a way that it can facilitate the solution of problems related to irrigation in an efficient way keeping in view the limitation of people behaviors.

Environmental Sustainability:

Water scarcity, pollution, and other water-related environmental and ecological problems have been increasing rapidly in many areas of the world. The environment takes into account the water source, land and air systems that support human production activities.  As water demands in agricultural, municipal, and industrial uses change over time, because of policy and technological changes, among others—the relationship between water use and the environment needs to be continually reviewed and adapted. In river basins where irrigation is the major water use, sustainable water management should ensure a long-term, stable, and flexible water supply to meet crop demands, as well as growing municipal and industrial demands, while at the same time mitigating or preventing negative environmental consequences from irrigation.

A guiding criterion for sustainable irrigation water management is to minimize the interference of the irrigation system with the associated environmental system, including the effects on the water bodies that receive irrigation water through wind-drift, surface runoff, or drainage to groundwater. In addition, to sustain irrigation profit over the long term, irrigation water management must meet legislative requirements with respect to the environment.  Indicators for environmental system integrity fall into three categories:

1. Health of aquatic and floodplain ecosystems. Extensive irrigation can affect drinking water health as indicated by bacteria, nutrients, and toxic contaminants, and soil health as indicated by the soil’s water-holding capacity, total organic Nitrogen and Carbon, PH value, and the conditions of surface aggregates.

2. Water quality. Irrigated agriculture affects water quality in several ways, including higher chemical- use rates associated with irrigated crop production, increased field salinity resulting from applied water, accelerated pollutant transport with drainage flows, groundwater degradation due to increased deep percolation to saline formations, and greater in-stream pollutant concentrations due to flow depletion.

3. Soil degradation. Irrigation is responsible for water logging and salinity in many regions where drainage systems are poor. The irrigation with traditional furrow systems may cause soil erosion that can be measured by the extent of topsoil losses. Thus, the adverse environmental effects of irrigation (such as water logging and salinization, groundwater pollution, and soil erosion) are often cumulative and may develop to an irreversible state because of long-term poor irrigation management. The measure of these indicators should be connected to both the short-term irrigation practices and performances and the long-term dynamic transmissions through some physical processes.