by Şükrü Esin
Soil salinity is a serious environmental problem affecting 20% of total irrigated land across the globe.
Harran Plain has the biggest groundwater reserve in the Middle-East and the largest irrigation field in the Southeastern Anatolia Project region which is 3700 square km drainage area, 1500 square km plain area and 476000 hectares of irrigation area. Crop pattern is very poor: about 70% is just cotton planting. There is a big problem with the salinization in this area since the Turkish State Hydraulic Works Directorate (DSI) irrigation project started.
The main average temperature is 18.88oC and the annual rainfall is about 300 mm, with evaporation reaching as high as 2023 mm. The highest evaporation occurs generally in July and the lowest in February. Rain is irregular and mostly falls in winter. But the area receives almost no rainfall between June and September.
Graph: Local Growing Seasons (Resource: New LocClim)
Harran plain is arid area and cotton the main crop. This graph shows the six months of dry period, nearly one month of moist and four months of humidity. What it basically means long dry summer with very low precipitation in the plain.
The water budget for the Harran Plain, as reported by the Turkish State of Water Works for the year 2000, reveals that water entering the plain for irrigation is about 1208 million cubic meters and precipitation contributes about 104 million cubic meters.
The losses of water from the plain occur in two ways: (1) evapotranspiration accounting for about 996 million cubic meters, (2) discharge as runoff and drainage resulting in 193 million cubic meters.
The annual rate of water storage in the plain is about 121 million cubic meters. The stored water stays in the system and increases in groundwater level, especially from the south to the middle north of the plain (Özgür et al., 2001). Currently, about 15% of the plain is salt-affected and 30% of it has a shallow water table able to develop salinity-related problems (Cullu et al., 2002).
The Effect of Climate Change on Harran Plain
Global Clime Change scenarios show that south east Turkey will have less precipitation and the summer will be longer. The Harran plain in southeastern Turkey then, will have less precipitation and more hot days in the future according to IPCC Global Climate Change prediction report.
Despite of all suggestions, farmers not willing to change irrigation methods as well as government does not want to decrease the funding for cotton plant.s This high income persuades the farmers to plant this crop every year.
According to IPCC Global Climate Change reports, that people are using water (almost 65%) for irrigation around the world. In Turkey that percentage is higher than the average. It is about 72% for agricultural irrigation. That´s why the State Hydraulic Works Directorate needs to change irrigation policy regarding this report. Also DSI should help farmers to develop modern irrigation methods and prepare themselves for 2100 scenarios action plan.
The Harran plain lies in the cradle of one of the world’s oldest civilizations that flourished between the rivers Euphrates and Tigris.
In 1996, planned irrigation came to Harran Plain in southeast Turkey. It was expected to bring a lot of benefits to agriculture in the region. Between then and 2012, the area under irrigation has increased from 35,000 to 150,000. However, the irrigation has been excessive and more than 10% of that land has been lost to salinization already. A much greater area is under threat of following suit.
Experts point out that the irrigation systems introduced in the region comprise mostly of open channels, and are therefore bound to fail given the topography and the climate. Annual evaporation losses in Harran are five times the annual rainfall. Under such conditions, open irrigation systems are bound to lead to soil salinization. Closed systems such as pipelines and drip irrigation systems are much more suitable, and much necessary in order to prevent degradation of land and hardship to farmers.