Akademik Veri Yönetim Sistemi
WATER RESOURCES OF TURKEY, cilt.2, ss.257-302, 2020 (SCI-Expanded)
Turkey is located in a semi-arid region. Due to topography, geological conditions, sea effect and the geographical position of the country, distribution of precipitation has shown temporal and spatial variability. Consequently, soil and water resources in the 25 river basins are not distributed evenly over the country. Therefore, irrigation is a prerequisite in order to develop a highly productive agricultural system, as well as to optimize agricultural production. Turkey has a total of 25.85 million hectares (Mha) irrigable area, of which 22.6 Mha land can be envisaged as economically and technically irrigable under today's conditions. Based on the soil, topography and drainage conditions, the national governmental agency-State Hydraulic Works (DSI)-responsible for development of soil and water resources including irrigation in Turkey set a goal nearly 60 years ago that 8.50 Mha area had been economically and technically irrigable under the available technology. Of the targeted irrigable area, as of 2017, 6.57 Mha land was equipped with irrigation facilities, 65% of which was constructed by DSI. Four major irrigation organizations were emanated for operation and maintenance services of rrigation schemes. As of the end of 2017, 4.28 Mha gross area (net 3.37 Mha) was equipped with irrigation facilities constructed by DSI; 73% of net irrigation area constructed by DSI was transferred to water user associations (WUAs). 15% was operated by irrigation cooperatives (ICs) and the remaining 12% by DSI. In order to increase the sizes of agricultural enterprises and decrease the average parcel numbers of undertakings, implementation of land consolidation (LC) projects in agricultural areas is necessary. Implementing LC projects before irrigation construction renders at least 40% savings in expropriation and construction costs. It also helps irrigation managers to increase the very low irrigation efficiencies (average 37%) and irrigation ratios (42% in DSI operated, 66% in WUAs operated irrigation schemes). As of the end of 2017, totally 54 BCM water was consumed in irrigation, domestic and industrial sectors. Of this, a total of 74% was consumed by irrigation such that 56% (30.2 BCM) was supplied from surface water resources and 18% (9.8 BCM) from groundwater resources. Regional development projects regarding irrigation have an important role so as to eliminate in inter-regional differences in terms of development. In this regard, The Southeastern Anatolia Project, i.e. the GAP, is considered as one of the biggest integrated regional development projects in the world. The GAP is a brand name of Turkey and contributes widely to increase the agricultural production of Turkey. After the completion of the GAP components, 1.79 Mha area will have been equipped with irrigation facilities. Net agricultural income has increased about four-fold in the GAP irrigation areas. However, it was observed that gross domestic agricultural product increased about six-fold in the GAP areas due to the irrigation practices. Irrigation return flows need monitoring in order to take preventive measures on time.