**1. Introduction**

The catchment area becomes transboundary when it extends between two or more countries [1]. In addition to being numerous in West Africa, transboundary watersheds are often the primary water resources of the countries that border them [2]. The transboundary situation of these basins causes a fundamental problem when considering the management of shared natural resources. In many cases, an

ecosystem divided by a political-administrative boundary is managed in a fragmented and sometimes contradictory way by the states that share it. This is due to the fact that sometimes states have different political priorities and environmental regulations [3].

At the end of the 1960s and the beginning of the 1970s, recurrent dry spells and climate change severely impacted agricultural production in the Kayanga/Geba basin, where the essential part of the population's income traditionally comes from rainfed crops in the uplands and rice cultivation in the lowlands, in addition to the livestock. To overcome this problem, the state of Senegal has adopted policies for the development and management of water resources in order to improve water management, boost socio-economic activities by increasing agricultural productivity, both in the rainy season and in the off-season, and promote local development [4, 5]. This is how the Agricultural and Industrial Development Company of Senegal (SODAGRI in French) created in 1974, was entrusted with the management of the three phases of the development of the Anambe basin, the central part of which is a vast flood basin of almost 16,000 ha [6]. The Anambe is the main tributary of the Kayanga/ Geba in Senegal. The developments are for hydro-agricultural and pastoral purposes with integration of agriculture, livestock, and continental fishing. In total, two dams have been built for this purpose in addition to the one set up by the Local Small Scale Irrigation Support Project (PAPIL in French).

In Guinea-Bissau, no hydro-agricultural development has been carried out. The Kayanga/Geba and Koliba/Corubal rivers are the main source of surface water in this country. It shares the Koliba/Corubal with Guinea. The other rivers are deeply penetrated by the tide.

The developments in the Senegalese part of the basin may run counter to the benefits that can be derived from harmonious use of water resources and cooperative management at the scale of the hydrological system. Because managing at this scale means ultimately taking advantage of the comparative advantages of each part of the hydrological system and respecting its total productive capacity [2]. This article aims to analyse water control and transboundary cooperation around the Kayanga/Geba river basin. It is a modest contribution to the analysis of the challenges of transboundary basin management in West Africa.
