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Naili Ozer 1 , Ali Fuat Demirel 2 1 Section Manager, General Directorate of State Hydraulic Works 2 Agricultural Engineer, General Directorate of State Hydraulic Works. Introduction Harran Plain is almost 200 000 hectares and recently 130 000 hectares of it irrigated from the source of Atatürk Dam and the rest of the area is under construction for irrigation. So far, there are three relevant reports prepared by the General Directorate of State Hydraulic Works. The first report is Lower Euphrates Project Urfa - Harran Plain Planning Land Classification Report which covers 200 561 hectares of land, the second is Southeast Anatolia Project Urfa - Harran Plain Planning Drainage Report which covers the same land with the previous report and the third report is Lower Euphrates Project Akçakale Ground Water Irrigation Detailed Land Classification and Drainage Report which covers 5 000 hectares of land. Based on the reports mentioned above, characteristics of soil, topography, salinity and alkalinity, and ground water are given in the following paragraphs. 1. Topography The general direction of the slope in the plain is from north to south and varies between 0-2 %. Surface slope is rather flat around Harran and Akçakale Towns and low-lying areas cause outlet problem. Slopes in the north are mostly higher than that of the south part of plain and surface and subsurface drainage problems are rarely encountered. Soil Characteristics : The soils of the plain are alluvial and residual. Soil profiles are deeper than 150 cm in 77 % of the area and in the rest of the area, they are shallow and underlying materials are sand, gravel, lime and rock. Land classes are given in Table 1. 95 % of soils have heavy texture in tillage layer and only 5 % of soils have medium texture also sublayers of soils are heavy textured. Soil colors are mostly brown and reddish brown. pH values are mostly between 7,5 and 8,0. Hydraulic permeability of disturbed soil samples vary but values are mostly higher than 0.5 m/day. Hydraulic permeability values were found between 0,22 and 3,51 m/day by using Auger-Hole Method at Akçakale Ground Water Irrigation area. According to the survey done in the years of 1964 and 1965, total soluble salt values were found between 0,100-0,200 % in 5 406 ha, 0,200-0,400 % in 4 604 ha, 0,400-0,600 % in 1769 ha and more than 0,600 % in 23 ha of land has ESP values more than 15.  Akçakale Groundwater Irrigation area ( 5 000 ha ) is located in the south part of the Harran Plain. even though there were 0,100-0,200 % TDS in 274 ha, 0,200-0,400 % TDS in 50 ha and there are no sodic soils in the project area. According to surveys carried out between 1990 and 1993, TDS values were found as follow: 0,100-0,200 % in 1 428 ha, 0,200-0,400 % in 1 099 ha, 0,400-0,600 % in 130 ha and ESP values were found to be higher that 15 % in this 86 ha land also. In order to monitor salinity changes, 62 locations were selected and soil samples taken from these locations by drainage engineer from Şanlıurfa Regional Directorate of DSI, in 2000. The results of the analyses show that salt content was increased in 29 % of the soils. Existing Structures Related With Irrigation and Drainage : Şanlıurfa -Harran Plain is irrigated with the water taken from Atatürk Dam Reservoir by Şanlıurfa irrigation tunnels. Construction of the irrigation and main drainage system and related components has been mostly completed in about 130 000 ha. Also subsurface drainage system is being constructed by GDRS at the south part of the plain. 2. Drainage Requirement Climate : Climate is arid and semiarid in the project area. Annual rainfall is about 300 mm in most of the plain but it is 460 mm in Şanlıurfa. Precipitation mostly occurs in winter and spring. Annual evaporation is 1 900 mm. Comparing the precipitation and evaporation values, it is understood that irrigation is absolutely necessary for most agricultural crops. Rainfall is not an important factor in drainage. Streams and Floods : The main stream is Cullap Creek in the project area. Cullap Creek bed is used as a main discharge channel and discharge capacity is expanded by the development. It can be said that there is no risk of flooding in the area. Irrigation : Trapezoidal open irrigation canal system has been built and mostly furrow irrigation method is used in the project area. Proposed crop pattern could not be realized and mostly cotton (approximately 85 %), some vegetable species and cereals are being grown in irrigated area. Irrigation water quality class is C2S1 and it is very good compared to the quality of the most of the other irrigation projects. With TAM values being used and MAD being taken as 70 %, RAM value for the root zone was calculated to be 110 mm. The reason of drainage problem is irrigation. The causes are given below: - Excessive water use, - Lack of knowledge about irrigation and agriculture, - Carelessness about irrigation and drainage structures. Seepage : There is no seepage from the adjacent areas because there is no existing irrigation and also adjacent high areas don't have soil depth enough to store moisture. There could be some leakage and seepage from irrigation canals because of deterioration. Groundwater : According to data taken from the Southeast Anatolia Project Urfa-Harran Plain Planning Drainage Report there were ground water problem (0-2 m) in 2 747 ha of land located in the south part of the plain and near Akçakale and Harran Towns urban areas. In Akçakale Ground Water Project area; ground water problems were observed in 2 160 ha (0.00-1,00 m ), 309 ha ( 1,00-1,50 m ) and 206 ha ( 1,50-2,00 m ) within the period of 1990-1993. According to the observations made in 2001 by DSI Operation and Maintenance Department, ground water problems were found to be increasing. 768 observation wells are augured to represent approximately 100 000 ha. In the peak irrigation period (July, 2001), depth of the groundwater was observed to be between 0.00-1.00 m in 5 195 ha and 1,00-2,00 m in 35 583 ha. Ground water analyses show that 83 % of the electrical conductivity values of the water is less than 2 500 micromhos/cm. Conclusion According to the survey results in the years of 1964 and 1965, there were 11 769 ha saline and and only 23 ha alkaline soils in the area. Ground water problems ( 0-2 m ) were encountered in 2747 ha. Akçakale Groundwater Irrigation area ( 5000 ha ) is taking place in the south part of the Harran Plain even though there were 0,100-0,200 % TDS in 274 ha, 0,200-0,400 % TDS in 50 ha and no sodic soil in the project area According to surveys has been done in the period from 1990 to 1993, 1 428 ha of land contains 0,100-0,200 % TDS, 1 099 ha of land contains 0,200-0,400 % TDS, 130 ha of land contains 0,400-0,600 % TDS, and 86 ha of land has ESP higher than 15 %. To observe the salinity changes 62 location were selected and soil samples taken by drainage engineer from Şanlıurfa Regional Directorate of DSI, in 2000. The analyze results show that 29 % of the soils salt content were increased. According to observation done by DSI Operation and Maintenance Department in 2001, ground water problems are observed to be increasing. 768 observation wells were augured to represent approximately 100 000 ha. In the peak irrigation period (July, 2001), depth of the groundwater was observed to vary between 0.00-1.00 in 5195 ha and 1,00-2,00 m in 35 583 ha (DSI., 2002). According to data collected, ground water and soil salinity problems have been increasing in irrigated area. Preventive Measures and Suggestions - Extension education is necessary for water users in irrigated agriculture, - Main drainage network must be examined and developed if necessary, - Subsurface drainage system should be constructed wherever it is necessary, - Infrastructures, such as land leveling and surface inlets, must be completed, - Real cost of water should be charged in volume base from water users. References . DSI, 1971. Aşağı Fırat Projesi Urfa Harran Ovası Planlama Arazi Tasnif Raporu, Devlet Su İşleri Genel Müdürlüğü X. Bölge Müdürlüğü, Ankara, Turkey. . DSI, 1978. Güneydoğu Anadolu Projesi Urfa-Harran Ovası Planlama Drenaj Raporu, DSİ Basım ve Foto-Film İşletme Müdürlüğü Matbaası, Ankara, Turkey. . DSI, 1997. Aşağı Fırat Projesi Akçakale YAS Sulaması(Güneren-Şemsettin-Birmuavi YAS Sulamaları) Ayrıntılı Arazi Sınıflandırma ve Drenaj Raporu, Devlet Su İşleri Genel Müdürlüğü XV. Bölge Müdürlüğü, Şanlıurfa, Turkey. . DSI, 2002. Şanlıurfa-Harran Sulaması 2001 Yılı Tabansuyu İzleme ve Değerlendirme Raporu, Unpublished Report. Devlet Su İşleri Genel Müdürlüğü İşletme ve Bakım Dairesi, Ankara, Turkey. |