Question: What body of water forms the western border of the 2010 Sahel famine country with the lowest population density ?

text: 2010 Sahel famine
Climate and vegetation overview

A large-scale, drought-induced famine occurred in Africa's Sahel region and many parts of the neighboring Sénégal River Area from February to August 2010. It is one of many famines to have hit the region in recent times. The Sahel is the ecoclimatic and biogeographic zone of transition between the Sahara desert in the north of Africa and the Sudanian savannas in the south, covering an area of 3,053,200 square kilometers. It is a transitional ecoregion of semi-arid grasslands, savannas, steppes, and thorn shrublands. The neighboring Sénégal River Area contains various vegetation types and covers parts or all of Mauritania, Mali, Senegal and Guinea. It has also had very low rainfall over the last year according to the UN, NGOs and the Senegal River Basin Development Authority. Sudan set a new temperature record of 49.7 °C (121.3 °F) on 22 June, in the town of Dongola.
Drought-hit nation Climate summary Population density per square mile Sahel state , Sénégal River-area state or CILLS member
Sudan Sudan straddles the Sahara , with only the Nile Valley and the small coastal region being available to agriculture and part of the Sudd flood plain lies in the south Water levels fluctuate up to 1.5 meters , depending on the intensity of seasonal flooding . and is mostly Sudanian savanna and sahel 43.7joint figure for both No
Southern Sudan South Sudan has got more tropical savanna and Sahel ecoregions and most of the Sudd flood plain lies in the north Water levels fluctuate up to 1.5 meters , depending on the intensity of seasonal flooding . and is mostly Sudanian savanna and sahel 43.7joint figure for both Sahel
Chad Chad is divided into three distinct zones , from the Sudanese savanna in the south , the Sahel in the central belt and the Sahara Desert in the north . The most fertile land is around the steadily shrinking Lake Chad 20.8 Sahel and CILLS
Central African Republic The climate of the C.A.R . is generally tropical . The northern areas are subject to harmattan winds , which are hot , dry , and carry dust . The northern regions have been subject to desertification , and the northeast is a desert . The remainder of the country is prone to flooding from nearby rivers as much of the southern border is formed by tributaries of the Congo River , with the Mbomou River in the east merging with the Uele River to form the Ubangi River . In the west , the Sangha River flows through part of the country . The eastern border lies along the edge of the Nile river watershed . The estimated amount of the country covered by forest ranges up to 8% , with the densest parts in the south . It is highly diverse , and includes commercially important species of Ayous , Sapelli and Sipo . The deforestation rate is 0.4% per annum , and lumber poaching is commonplace 18.4 No
Cameroon The climate varies with the terrain . The climate is exceedingly hot and humid , the coastal belt includes some of the wettest places on earth . For example , Debundscha , at the base of Mt . Cameroon , has an average annual rainfall of 405 inches ( 10,287 mm ) . The coastal plain extends 15 to 150 kilometres ( 9 to 93 mi ) inland from the Gulf of Guinea and has an average elevation of 90 metres ( 295 ft ) . Exceedingly hot and humid with a short dry season , this belt is densely forested and includes some of the wettest places on earth , part of the Cross-Sanaga-Bioko coastal forests . The South Cameroon Plateau rises from the coastal plain to an average elevation of 650 metres ( 2,133 ft ) . Equatorial rainforest dominates this region , although its alternation between wet and dry seasons makes it is less humid than the coast . This area is part of the Atlantic Equatorial coastal forests ecoregion . An irregular chain of mountains , hills , and plateaus known as the Cameroon range extends from Mount Cameroon on the coast - Cameroon 's highest point at 4,095 metres ( 13,435 ft ) - almost to Lake Chad at Cameroon 's northern tip . This region has a mild climate , particularly on the Western High Plateau , although rainfall is high . Its soils are among Cameroon 's most fertile , especially around volcanic Mount Cameroon . Volcanism here has created the crater lakes , like Lake Nyos of the Cameroonian Highlands forests ecoregion . The southern plateau rises northward to the grassy , rugged Adamawa Plateau . This feature stretches from the western mountain area and forms a barrier between the country 's north and south . Its average elevation is 1,100 metres ( 3,609 ft ) , and its temperature ranges from 22 °C ( 71.6 °F ) to 25 °C ( 77 °F ) with high rainfall . The northern lowland region extends from the edge of the Adamawa to Lake Chad with an average elevation of 300 to 350 metres ( 984 to 1,148 ft ) . Its characteristic vegetation is savanna scrub and grass . This is an arid region with sparse rainfall and high median temperatures 102.8 No
Nigeria Nigeria is covered by rainforests over the southern third , Guinean forest-savanna mosaic in the middle third and both savannas and Sahel in the northern third . The mountain land is also found in the mountains near the Cameroonian border . The most southerly part of the forest , especially around the Niger River and Cross River deltas , is mangrove swamp ( see Central African mangroves ) . North of this is fresh water swamp , containing different vegetation from the salt water mangrove swamps , and north of that is rain forest 433.8 Sahel
Niger Niger 's subtropical climate is mainly very hot and dry . Niger is located mostly in the Sahara desert save for a small piece of tropical savanna around the River Niger basin . Some flat to rolling savanna and Sahel land is in the southernmost fifth of its territory and in the northern hills 31.2 Sahel and CILLS
Burkina Faso A relatively dry tropical savanna , the Sahel extends beyond the borders of Burkina Faso , and borders the Sahara to its north and the fertile region of the Sudan to the South . Situated at a middle latitude is the Sudan-Sahel region , a transitional zone for rainfall and temperature levels . Further to the south , the Sudan-Guinea zone receives more than heavy rain each year and has cooler temperatures . The northern fringes of the country are beginning to become a desert 148.9 Sahel and CILLS
Côte d'Ivoire /Ivory Coast Côte d'Ivoire 's terrain can generally be described as a large plateau rising gradually from sea level in the south to almost 500 m elevation in the north . In the south of Côte d'Ivoire is marked by coastal inland lagoons that starts at the Ghanaian border and stretch 300 km ( 186 mi ) along the eastern half of the coast . The south and southwest of the country are covered with dense tropical moist forest like the Eastern Guinean forests and Western Guinean lowland forests that cross the Sassandra River . The mountains of Dix-Huit Montagnes region are home to the Guinean montane forests . The Guinean forest-savanna mosaic belt extends across the middle of the country from east to west . The North is part of the West Sudanian savanna , a savanna -and- scrubland zone of lateritic or sandy soils , with vegetation decreasing from south to north . The terrain is mostly flat to undulating plains , with mountains in the northwest . The climate of Côte d'Ivoire is generally warm and humid , ranging from equatorial in the southern coasts to tropical in the middle and semiarid in the far north . There are three seasons : warm and dry ( November to March ) , hot and dry ( March to May ) , and hot and wet ( June to October ) . Temperatures average between 25 and 32 °C ( 77.0 and 89.6 °F ) and range from 10 to 40 °C ( 50 to 104 °F ) 165.6 No
Mali About two-thirds of Mali is located in the Sahara desert , exempt for the southeastern third , which contains both a Sahel zone and fertile tropical savanna around the River Niger 30.3 Sahel , CILLS and Sénégal River Area
Algeria The coastal quarter has a Mediterranean climate , while the rest is either a sandy desert or semi-desert on the interior 's few hills . There is a strip of Sahel running through the far south and the climate is cooler in the mountain regions 37.1 Sahel
Mauritania Mauritania is located mostly in the Sahara desert save for a small piece of tropical savanna and Sahel around the River Senegal in approximately the southernmost quarter of its territory . Because of extended , severe drought , the desert has been expanding since the mid-1960s . To the west , between the ocean and the eastern plateaus , are alternating areas of clayey plains and sand dunes , some of which are shifted from place to place by high winds 8.2 Sahel state , CILLS and Sénégal River Area
Senegal Senegal has a both Sahel , Sahel-Soudan , Sudan_ ( region ) , Soudan-Guinea , tropical rainforest , and Guinean mangroves . Most of the southern Casamance arm of the country has been classified by the World Wildlife Fund as part of the Guinean forest-savanna mosaic ecoregion 180.4 Sahel state , CILLS and Sénégal River Area
Gambia The Gambia has a subtropical climate with distinct cool , dry and hot , humid seasons . The temperature escalates rapidly on going inland and has been known to reach as high as 51 °C on occasions . The average annual rainfall ranges from 920 mm ( 36.2 in ) in the interior to 1,450 mm ( 57.1 in ) along the coast . The grassy flood plain of the Gambia River , which contains Guinean mangroves near the coast , with West Sudanian savanna upriver and inland 425.5 CILLS and Sénégal River Area ( observer member )
Guinea Guinea has both lowland belt running north to south behind the coast ( Lower Guinea ) , which is part of the Guinean forest-savanna mosaic ecoregion ; the pastoral Fouta Djallon highlands ( Middle Guinea ) ; the northern fertile ( Upper Guinea ) ; and a south-eastern rain-forest region ( Forest Guinea ) 106.1 Sahel state , CILLS and Sénégal River Area
Guinea Bissau The climate in Guinea-Bissau is tropical and is generally hot and humid . It has a monsoonal-type rainy season with southwesterly winds and a dry season with northeasterly Harmattan winds . It is warm all year around and there is little temperature fluctuation ; it averages 26.3 °C ( 79.3 °F ) . The average rainfall for Bissau is 2,024 millimetres ( 79.7 in ) although this is almost entirely accounted for during the rainy season which falls between June and September/October . From December through April , the country experiences drought . The terrain of Guinea-Bissau is mostly low coastal plain with swamps of Guinean mangroves rising to Guinean forest-savanna mosaic in the east 115.5 CILLS