The FAO, in collaboration with the Ministry of Water Resources and Irrigation and the Ministry of Agriculture and Land Reclamation , has recently launched the project “Support sustainable water management and irrigation modernization for newly reclaimed areas.” This project will increase the efficient use of resources to achieve high productivity at low input level, while minimizing adverse external factors.They also focus on managing the ecological, social, and economic risks associated with production systems in the agricultural sector, including disease and climate change.The project will also focus on identifying and increasing the role of ecosystem services, especially regarding their effects on resources utilization, risk response and preserving the environment.As the freshwater availability from the Nile river is decreasing, farmers are using low-quality groundwater for irrigation instead.It results in increased soil salinization thereby negatively impacting crop yields and quality.Therefore, it is essential that Egypt regulates the reuse of drainage water to control soil salinization.This will require a robust salinity monitoring program that can provide updated information on the quality and quantity of drainage water and groundwater.Most importantly, these data are vital in developing strategies for the safe use of these waters.Like many other countries, Egypt needs to prepare comprehensive guidelines for the use of poor-quality drainage and groundwater for irrigation,indoor vertical farming considering soil types, climatic conditions, and crops to be grown.
For the coastal areas where salinity levels are very high, the use of salt-tolerant crops and halophytes must be encouraged.Despite vast salt-affected areas in Ethiopia, research and development projects that address salinity are mostly absent.Consequently, the current and future extent of salt-affected soils are unknown, whereas economic implications are not brought to the attention of policy makers.No country organization monitors, evaluates, and permits for expanding irrigation or to discontinue existing irrigated farms.Available information is limited and is based on preliminary studies that are incomplete in most cases or comes from outside Ethiopia.The country lacks a systematic analysis of salt-affected areas and its strategic plan that addresses soil salinization and sodification.Such a project should lead to sustained funding of soil salinity research that assesses the quantification of its extent and damage, as well as the development of technologies and management practices that reclaim and prevents further expansion of soil salinity in the country.Specifically, the introduction of adequate drainage systems must be considered, and irrigation water conveyance channels should be lined to reduce water losses, especially in areas of saline groundwater.In addition, the selection of salt-tolerant forages, crops and legumes could largely improve the productivity of salt-affected lands.In summary, Ethiopia must develop a long-term national policy and strategic plan that leads to lasting solutions for its irrigated agriculture.Another significant development in this region is the construction of the world’s largest dam on the Nile River by Ethiopia.The Grand Ethiopian Renaissance Dam , on the River Nile near the Sudan border will have a reservoir capacity of 70Bm3and an electricity generation capacity of 6000MW.It is estimated that GERD will irrigate 1680 km2 forest land in the northwest of Ethiopia.
Ethiopia claimed that this dam would also benefit the downstream countries mainly Sudan and Egypt by removing 86% of their silt and sedimentation load and conserving water by regulating flow that will allow reliable all-season water supply to Sudan and Egypt.Although Ethiopia claims that there will be no consequences for downstream users such as Egypt.There are concerns that GERD will reduce 12–25%of Nile flow into Egypt especially during the dam filling period of 5–7 years.This will have severe consequences for optimal crop production and management of soil salinization in Egypt.Therefore, the cooperation between the Nile water-sharing countries is essential for the management and protection of this vital water resource to ensure future food security and livelihood of the 280 million people living in the Nile basin.Irrigated agriculture in Pakistan is mainly confined to the Indus plains where it has been developed by harnessing major water resources available to the country.The agriculture in the arid and semi-arid areas of Pakistan largely depends on sustained irrigation supplies, as the evapotranspiration demand is high, and rainfall is either inadequate or unreliable.The contiguous Indus basin irrigation system irrigates an area of about 16 million ha , diverting annually 131 billion m3of surface water to 43 main canal systems.The perennial water supply is available to 8.6Mha while the remaining area receives water only during the summer season.About 93% of the total water withdrawal is allocated to the agricultural sector, 4% is used for domestic purposes and the rest 3% goes to industrial use.The large-scale irrigation development in the Indus Basin was initiated in the second half of the 18th century to expand the settlement opportunities, avoid crop failure and famine.At that time, the groundwater levels were below 30m from the soil surface, and therefore drainage needs were not considered.Due to persistent seepage from unlined canals and percolation from irrigated fields, the groundwater table rose to within 1.5m of the soil surface, creating waterlogging and, consequently, soil salinity problems.The problems of soil salinity became more noticeable in areas where groundwater was saline.
Most of the soil salinity in the Indus basin comes from primary salinization.However, secondary salinization using poor-quality groundwater for irrigation has further compounded the problem.The Indus basin is faced with a considerable salt balance problem.The average annual salt inflow by the Indus river water is estimated to be 33 million tons , while the outflow to the sea is only 16.4Mt.The average annual salt storage of around 16.6 million tons is equivalent to 1ton of salts per hectare of irrigated land.Therefore, saline soils have become an important ecological conundrum with 4.5Mhaalready afflicted.As illustrated in Fig.35, the salinity problems in Sindh are most severe where about 50% of the irrigated area is affected.This is mainly due to poor drainage conditions, shallow saline groundwater, and the use of poor-quality groundwater for irrigation, as surface water supplies are far less than the actual crop water requirements.In addition to total soil salinity in the Indus basin, sodicity is a major problem because 70% of all groundwater wells in the basin pump sodic water, affecting soil structure and infiltration rates.Salt-affected soils of the Indus basin are usually classified into four types as shown in Table 6.The combined threats of water logging and soil salinization were recognized as early as 1870, and since then various remedies have been undertaken to overcome this twin menace.These include engineering solutions, reclamation strategies,hydroponic vertical farming and biological interventions.These are briefly discussed below.Engineering solutions—The first detailed survey of groundwater table depth and salinity was conducted in the 1950s with the collaboration of the US Geological Survey.It formed the basis for public sector vertical drainage program through Salinity Control and Reclamation Projects.As a result, in both fresh and shallow groundwater areas, 14,000 tube wells with an average capacity of 80 L s 1 were constructed between 1960 and 1970, covering 2.6Mha of irrigated land with an estimated cost of US$ 2 billion.This program was aimed at lowering the groundwater table and increasing irrigation supplies at the farm gate by mixing pumped groundwater with fresh canal water.The SCARPs were partially successful in arresting water logging and salinity by lowering groundwater tables below 1.5m in 2.0Mha and below 3m in 4.0Mha.As a result, areas with soil salinity decreased from 42% in 1960 to about 32% in 1977–79, and improved irrigation supplies allowing increased cropping intensities from 84% to 125% in most SCARP areas.In the 1970s, one realized that circulating salt-contaminated water through vertical drainage aggravated the salinity problem, thereby shifting to constructing horizontal drainage systems that were 10 times more expensive.The main argument in favor of horizontal drainage was that drainage water quality would improve over time, allowing more of it to be used for irrigation as well as reducing disposal problems.Since then, about 10 major horizontal drainage projectshave been completed in different parts of Pakistan.The major bottleneck in the successful operation of these drainage systems was the safe disposal of saline drainage effluent.To overcome this, Pakistan constructed a 2000 km long surface drain on the East side of the Indus River, moving drainage waters of more than 500,000 ha of land to the sea.
Reclamation strategies—The salinity management in Pakistan remained focused on lowering of groundwater table and leaching of salts, without a national action plan for reclaiming sodic and saline-sodic soils.Efforts by local governments were mainly confined to supporting field-level research and providing subsidies to the farmers for gypsum application.The use of gypsum, acids, and farmyard manure, in combination with surface scarping and deep plowing were extensively applied.Agricultural and industrial wastes such as farmyard manure and sugar industry byproducts have also been used to improve sodic soils.A large range of acid materials was tested in Pakistan including sulfur, sulfuric acid, and aluminum sulfate.However, due to their cost and management complexities, farmers deemed these less attractive.Instead, gypsum was considered the most cost-effective additive for the reclamation of sodic soils and is heavily subsidized by the government.Biological interventions—The biological approach emphasizes the use of highly saline water and lands on a sustained basis through the profitable and integrated use of the genetic resources embedded in plants, animals, and improved agricultural practices.In Pakistan, a considerable amount of work has been done to use highly saline waters for growing salt-tolerant crops.This includes the planting of salt-tolerant plants, bushes, trees, and fodder grasses.Plants, particularly trees, are commonly referred to as biological pumps and play an important role in the overall hydrological cycle for a given area.In Pakistan, bioremediation was promoted as a valuable tool for controlling rising water tables and salinity, through enhanced evapo-transpiration.During the last 20 years or so, many salt-tolerant species and varieties have been developed in Pakistan, such as poplar, eucalyptus, tamarix, maskit and acacia.Similarly, non-woody plants such as bushes, sedges, grasses, and herbs can develop deep-rooted systems that can use shallow groundwater.However, their ability to maintain low water tables is expected only when these plants occupy a sufficiently large area.During the last 2 decades, Pakistan has made significant efforts to control soil salinization, which has reduced the saline area from over 6Mha in 1970s to 4.5Mha in 2007.Despite these massive investments over the last 3 decades, soil salinization remains the biggest challenge for the Indus basin.It continues threatening the sustainability of its agricultural system and the capacity of Pakistan to feed its growing population.Much discussion is focused on future water shortages and the need for adequate drainage of the Indus basin.The salt management issues in Pakistan are complex, and therefore an integrated approach is a key for sustainable irrigated agriculture.Irrigation and drainage are closely linked because excess irrigation is the main cause of water logging while the level of irrigation management dictates the amount of effluent disposal.Drainage water disposal will remain a major issue for effective salinity management in Pakistan.Disposal of saline effluent in rivers merely transports the salts to irrigated lands at the tail end of the irrigation system.It is therefore neither a practical nor environmentally friendly long-term solution.Due to the siltation of main reservoirs, the water storage capacity of Pakistan is expected to reduce by 57% by the year 2025 and to meet the future water requirements, 22Bm3 of more water will be needed.Furthermore, due to climate change effects, future unmet water demand is likely to reach 134 million m3 by 2050.Consequently, unless Pakistan significantly increases its freshwater use efficiencies, it will have to use more poor-quality irrigation water in the future.Also, it will need to seek sustainable re-use of drainage water to minimize drainage effluent.Timely availability of farm inputs such as salt-tolerant germplasm and promotion of saline agriculture through crop diversification can improve the capacity of individual farmers as well.Most importantly, farmers will need to have access to new information about improved irrigation management and reclamation approaches.The case studies of Section 15 illustrate the need for application of improved management practices for the major irrigated regions of the world.In this final section, we will synthesize the identified research priorities with these region-specific challenges and needs.Despite the large research and developmental efforts on salt-affected soils in the past, knowledge gaps remain, for new and innovative research and tools that will provide increasing resilience to salt-affected agriculture.Water moves through hydrologic cycles and always carries salts and other elements with it naturally, as it moves through the landscape into the oceans.It is therefore that salinity and water logging have impacted agricultural production in arid areas for more than 2000 years.