## 2 Study Site  
The Kilombero river is a tributary of the Rufiji river, one of the major basins in Tanzania, and is situated in the south-eastern part of the country (Figure 1). The Kilombero catchment covers an area of 40,240 km\({}^{2}\) with elevation ranges between 200 and 2500 m.a.s.l. [32]. The broad floodplain of the main Kilombero river comprises about 7967 km\({}^{2}\)[33] and is framed by the north-western Udzungwa mountains and the Mahenge Mbarika mountains in the south-east. The plain is geologically described by sedimentary basin infillings forming a seasonal alluvial floodplain geographic wetland type dominated by fluvisol soils [34]. The regional climate is characterized as sub-humid tropical with an average daily temperature of around 22-23 \({}^{\circ}\)C and annual precipitation of about 1200-1400 mm [35]. The bimodal rainy pattern comprises a short rainy season (November-January) and a long rainy season (March-May) with a distinct dry season from July until October. The Kilombero river is a natural shaped river with a high yearly discharge variability of about 92-3044 m\({}^{3}\)/s [36]--as observed at the Swero gauging station situated at the outlet of the catchment--and regular flooding of the wetland during the long rainy season. Land use and cover of the wetland are strongly attributed to the flooding duration, height and extent of the Kilombero river and its tributaries. The 2012 national population census [37] counted over 670,000 people living in the two districts of Kilombero and Ulanga, which occupy the valley and immediately adjoining hilly regions. Annual population growth was estimated respectively at 3.9% and 2.4% against a national rate of 2.7%. Over the last five decades, the valley (especially its NW section) has been a magnet for infrastructure development (including the TAZARA railway), resettlement, immigration and consequently an expansion of rural centers and farming [38]. A few large commercial firms and a large number of small farms grow mostly rice, maize and sugarcane. Furthermore, the floodplain is used for fisheries and cattle grazing [39]. The wetland ecosystem also provides other direct livelihood inputs like forest products, match grass, brick making, bush meat and domestic water [40]. In 2000, Tanzania ratified the Ramsar Convention of Wetlands of 1971. This agreement stipulates wise use of wetland resources, thereby maintaining the ecological character of the site while contributing to people's welfare [41]. In April 2002, the Kilombero Valley Floodplain Ramsar Site was designated under the Ramsar Convention as a wetland of international importance. This designation was justified by a range of ecological services, functions and values provided by the wetland, including the presence of the wetland dependent Puku Antelope _Kobus vardonii_ listed as near threatened in the IUCN Red List of Threatened Species; and its role as a dry season wildlife refuge for seasonally migrating species [42] moving between the Udzungwa mountain range in the North (where the Udzwungwa National Park and Kilombero Nature Reserve are situated) and the vast Selous Games Reserve situated to the south-west of the floodplain.