National Park dominates the south and includes much of the bay's islands, the southernmost of the bay and the southeasternmost parts of the park are not in the region, about a third of the region is a national park area. Nearly all of the country's islands and islets lies in this region and they include Echakcher, Kiaones, Niroumi, Nair, Arel, Tidra, the country's largest island, Kijji, Touffat, Cheddid and sometimes Serenni. Mauritania is mostly covered with desert, with only its western regions around the coast of Atlantic Ocean having some vegetation, along with the southern regions on the Senegal river. There are some oasis in the desert regions. Since it is a desert, there are large shifting dunes forming temporary ranges. The average elevation is around above the mean sea level. The rainfall in the northern regions closer to the Tropic of Cancer receives around of annual rainfall compared to the southern portions that receives around . The average temperature is , while during the night it reaches . Due to the geography, the inhabitants historically, have been nomadic. In modern times, people have migrated to urban centres during the drought in 1970 and 1980. There are a few sedentary cultivators, who are located only in the Southern regions of the country. Research has indicated that the Saharan movement has resulted in reduction of rains in the region from the 1960s, when it received close to of rainfall. Local administration The local administration is adopted from French local administration framework with the Ministry of Internal Control governing the local bodies. The original administration was held by Governors of each district, but after the municipal elections in 1994, the powers have been decentralized from the district bodies. Nouadhibou is one of 15 wilayas (regions). The smallest administrative division in the region is the commune. A group of communes form a moughataa (department) and a group of moughataa form a district. The executive power of the district is vested on a district chief, while it is on the hakem in the moughataa. The communes are responsible for overseeing and coordinating development activities and are financed by the state. The Local Governments have their own legal jurisdiction, financial autonomy, an annual budget, staff, and an office. The elections for the local government are conducted every five years along with Senate and Parliamentary elections. On account of the political instability, the last elections were