ENVIRONMENTAL CHALLENGES IN THE ORUMIYEH LAKE

The lake and its value

The Orumiyeh Lake is located in the north-west part of Iran at an elevation of 1,276 m asl, covering an area of 5,100 km2 and draining a “closed” catchment of over 50,000 km2. It is a hyper saline water body with an average depth of 5 m and volume of some 18 billion cubic meters (BCM). The salinity of the lake (about 260 g/l) is too high to support the diversity of aquatic fauna, except for algae and microscopic shrimps that are called Artemia. The microscopic shrimps are, however, the main reason of bird diversity and, particularly, the migration of Flamingos to this area. The lake area has been the national park since 1971, and the second Ramsar site since 1975. The lake is also surrounded by a number of saline and freshwater wetlands.

The total estimated surface water resources in the entire basin equate to 9 BCM (7 BCM surface water and 2 BCM groundwater). The average annual precipitation rate over the lake is approximately 250 mm, which corresponds to about 1.2 BCM. The annual average rate of water inflow to the lake is about 4.6 BCM. The average annual rate of evaporation from the lake surface is about 5.8 BCM, which is equal to the total input to the lake from rain and inflow. The existence of the lake is, therefore, dependent on the equivalent freshwater inflow. Reduced water inflow may lead to declining water levels and increasing the salinity concentration to levels exceeding the tolerance limits of Artemia. The loss of Artemia shrimp in turn may cause a decline in the number of birds which migrate to the lake. It also could lead to the loss of economical income of the local people selling Artemia. The decline of water level may expose the salty land, which leads to salty winds that are extremely damaging to the environment, and the 380,000 ha irrigated as well as the 420,000 ha rainfed land. All this will have an adverse impact on the 4.4 million people living in the basin.

Increasing water stress

The past two decades have seen an intensification of water resource and agricultural development in the basin. Future development may lead to the extension of irrigation by 235,000 ha, brining the total irrigated area in the basin to 615,000 ha. Due to the already existing development, the Orumiyeh Basin has suffered intensive and increasing water stress, which revealed itself through irrigation water deficit, rapid drawdown in some aquifers, a 3.5 m water level drop in the lake and a 7.3 km retreat of the shoreline during the recent droughts of 1988–2001, increasing salinity and crystallization of salt on the shores, and a significant decrease in Artemia and Flamingo populations in the lake and the surrounding wetlands. In the end of 2002 the salinity exceeded the tolerance level of the Artemia in the water, and it almost completely destroyed the shrimps, but fortunately some managed to survive in small pockets around the inlets of the largest rivers.
The Orumiyeh Lake Basin is relatively “rich” in water resources compared to many other semi-arid regions of Iran, but even here local and temporal water shortages occurred in all the key water user sectors, especially in the dry years, threatening both the unique ecosystem and the agricultural production. In the valleys, irrigated agricultural production provides an income to a large part of the population, producing mostly fruits and vegetables for the market. In the last decade, the irrigation needs could not be met in many cases at several locations. And with damages to orchards and agricultural lands, a serious depletion of groundwater resources occurred, including saltwater intrusion from Lake Orumiyeh.

The question of balance

The total annual gross water demand in the basin at present is estimated to be 4.4 BCM, of which agricultural demand is about 4.2 BCM and the balance is due to domestic requirements and industry. The projected total future demand for these sectors is about 6.4 BCM. The difference of 2 BCM between the present and the future water demand is mostly due to the increase in agricultural demand, which exceptionally healthy), it is necessary to ensure a long-term mean annual inflow of 4.6 BCM. The variability ofinflow between years and seasons will lead to Artemia losses and salt deposition at times (as has already occurred in the dry spells of 1998-
2002), but the damage may not be irreversible. In other words, the present condition shows that there is a fragile balance between the inflow and evaporation from the lake. But with future irrigation developments the inflow to the lake will be reduced by about one-third (future increase in water abstractions by 2 BCM). In such conditions, the inflow to the lake will be below the required threshold, which is up to (estimated) 70 percent of the time throughout the year on average. This will lead to frequent drops of lake salinity levels below the acceptable range of salt content (about 150–280 g/l for Artemia). The adverse environmental consequences of this are clear from the above, and the associated economic losses have to be quantified in order to ensure what decisions on future water resources development need to be taken. The challenge is to make a trade-off between water potential and the demands of different sectors in order to preserve the environmental sustainability in the region.
Improvement of irrigation efficiency in order to reach a more sustainable coexistence between agricultural and environmental demands seems to be the major task of water and demand management in this basin. The present irrigation efficiency is 30-35 percent, which leaves a lot of room for improvement and saving water that may ensure future irrigation development and satisfy environmental water demand of the Orumiyeh Lake.

Source: IWMI, Intl Water Management Institute