(June through September) is characterized by intense heat and alternating dryness and humidity, with temperatures exceeding . Temperatures are moderate from November to March, ranging from as high as in April to as low as in January. Rainfall averages per year, confined to the winter months, and falling in brief storms which are occasionally heavy enough to flood the small ravines and the usually dry wadis. Sudden, violent dust storms occasionally descend on the peninsula, blotting out the sun, causing wind damage, and temporarily disrupting transport and other services. The scarcity of rainfall and the limited underground water, most of which has such a high mineral content that it is unsuitable for drinking or irrigation, severely restricted the population and the extent of agricultural and industrial development the country could support until desalination projects began. Although water continues to be provided from underground sources, most is obtained by desalination of seawater. Wildlife Flora Although most of the country consists of sand deserts, a small part of the country houses different vegetation zones, where trees, reeds and shrubs like tamarind, phragmites, and mace can grow. These regions are mostly to the east, near the coast. The inherent limiting factor for vegetation growth is water availability. Certain geographical features partially alleviate this water scarcity, such as rawdas, which are large depressions found on the soil surface and which help recharge the aquifers. As these sites constitute the most easily obtainable sources of shallow groundwater, they are also among the areas most abundant in wild vegetation. In the south, where groundwater is exceedingly scarce, vegetation can found growing in wadis (dry river valleys) fed by run-off from nearby hills and in rawdas. Fauna There are 21 species of mammals that have been recorded in Qatar. Larger terrestrial mammals such as the Arabian oryx and Arabian gazelle are protected animals and are held in nature reserves. The Arabian gazelle is the only native gazelle species to Qatar and is locally referred to as 'rheem'. Qatar's territorial waters in the Persian Gulf are rich in marine life. Sea turtles nest en masse on the coastline from Fuwayrit to Ras Laffan. The Ministry of Environment (MME) carries out routine patrols of nesting areas to ensure their conservation. Dugongs are known to congregate off the country's coasts. In the course of a study being carried out in 1986 and 1999 on the Persian Gulf, the largest-ever group