Water efficiency and productivity is a top priority in Central Asia since water for irrigation is getting scarcer. For that, researchers argue, irrigation practices, among other things, need to be improved and infrastructure upgraded first. This is because inefficient water management also leads to waterlogging and salinization, a major problem in the region. In some areas, however, water is also lifted to the fields with pumps, a method known as lift irrigation. And this raises another issue: energy efficiency.
The International Water Management Institute (IWMI) has been working on these issues in Central Asia together with national partners and international research-for-development organizations for a number of years now. For example, IWMI launched a three-year project on lift irrigation in Uzbekistan in 2012 to increase water and energy efficiency in lift irrigation areas. It builds on another similar project carried out in the Fergana Valley, mainly in northern Tajikistan, where enormous amounts of water are pumped to the foothills. That significantly increases electricity use for irrigation and makes operation of pumps extremely costly.
The new project focuses on water transportation from the River Amu Darya to the Karshi Steppe, a region in southern Uzbekistan where water scarcity is being experienced and local communities are dependent on agriculture. It aims to identify new technologies for sustainable water and energy use in these areas and make necessary recommendations. Water transportation has helped to increase the irrigated area from about 50,000 to 325,893 ha. But today water shortages and degradation of agricultural lands have become a major concern. And the project pursues a multi-pronged solution, including efficient use of groundwater and optimization of energy and water consumption. The rationale is that groundwater is pumped for irrigation when needed, and the water table is replenished naturally when no irrigation takes place.
The project also involves studying water balance and water demand using remote sensing to collect data on land use and land cover (LULC) types in the Karshi Steppe. Data on changes in LULC is very important for water resource management, water supply planning, flood control and waste water treatment. Quantifying the LULC change rate is necessary for improving land and water management systems, agricultural resources and the wider environment.
The study, which was completed recently, determined LULC change dynamics in the Karshi Steppe, where the irrigated area grew drastically in the Soviet past. The researchers used images from the Landsat program, an enterprise for acquisition of satellite imagery of Earth, and ground truth data obtained through field visits. They examined the LULC change dynamics for five years: 1972, 1978, 1987, 1998 and 2011. To analyze land cover in the Karshi Steppe, the researchers employed two methods: supervised classification to classify crops, only for 2011 for which ground truth data was collected, and the Normalized Difference Vegetation Index (NDVI), for all other years. All available data was then fed into ArcGIS, a program for working with maps and geographical information.
Initial results show that a substantial change in land use has occurred since 1972. An area of 325,893 ha was under cultivation as of 2011 and different crops were grown. The researchers are now calculating levels of evapotranspiration, the sum of evaporation and plant transpiration, to determine how much water is evapotranspired and how much water local farmers actually need. Once results are in, they will identify the actual water requirements and suggest options to reduce any water and energy losses. These results will also be used to draw up recommendations for utilizing groundwater for irrigation. It is hoped that this will help to regulate the water table, increase water efficiency and reduce any losses. It will also help to tackle the problem of salinity as water will be used more efficiently.