The hydrology and hydrogeology of dambos: a review

Abstract

Dambos are shallow, seasonally waterlogged, tropical and subtropical African wetlands. Their importance, through their role in agriculture and water supply to downstream river networks, has been widely acknowledged. As a result, much research has been conducted on the hydrological functions of dambos and their hydrogeological structures, in an attempt to better understand, utilize and manage this regionally ubiquitous landform. However, these studies have resulted in little consensus regarding the geomorphology of dambos, their hydrological regimes and the hydrogeological model that drives those regimes. This review paper, focusing on dambo hydrology, hydrogeology and their primary determinants, highlights the key issues of the debate and draws some overriding conclusions from the divergent literature. Five hypotheses are proposed based on these conclusions, in an attempt to focus future dambo research efforts.

Inductively mapping expert-derived soil-landscape units within dambo wetland catenae using multispectral and topographic data

“…2). This area is representative of the geomorphology, climate, and vegetation regimes associated with African dambos (Mäckel, 1974;Acres et al, 1985;Mäckel, 1985;von der Heyden, 2004). The contemporary climate in this area is wet tropical with a mean annual precipitation of ∼ 120 cm (distinctly bimodal distribution), and a mean annual temperature of 23°C at an elevation over 1 km above sea level (Survey Department, 1967).…”

“…Radwanski (1959) mapped dambos as a single associate in the catena, and gave these wetland areas relatively little consideration. Since that survey was completed, a consensus has emerged in the literature regarding the distinction of the margin, floor and bottom landscape units within dambos (Mäckel, 1974;Acres et al, 1985;Mäckel, 1985;von der Heyden, 2004). Based upon the published literature both throughout Africa (cited above) and from Uganda specifically (Brown et al, 2006), we formally defined the margin class as having a slope N2% without meeting the subsoil color requirements of the upland class -as measured using handheld inclinometers in the field.…”

Creating local institutional arrangements for sustainable wetland socio-ecological systems: lessons from the ‘Striking a Balance’ project in Malawi

“…Wetlands exist in various forms throughout central Southern Africa, ranging from permanent and extensive swamps to seasonally flooded stream and river valleys, and grassland plains with seasonally high water tables known locally as dambos (Balek & Perry 1973;Thomas & Goudie 1985;Boast 1990;von der Heyden 2004). Estimates suggest that these wetlands account for between 2% and 4% of the total land area of Malawi, and some 12% of the total cultivable land area (Mloza-Banda 2005) and have long supported a range of important ecosystem services including the provision of water, fishing, grazing, seasonal agriculture and wild plant collection (Roberts 1988;Noble 1996;Wood & Thawe 2013).…”

The role of a dambo in the hydrology of a catchment and the river network downstream

“…Hence, some of the intrinsic hydrological functions leading to the perceived importance of the landform, such as the commonly held theory that dambos function as headwater sponges (Balek and Perry, 1973;Debenham, 1948) have been challenged (Bullock, 1992b;McCartney, 2000). Substantial contributions highlighting these differences are found in the reviews by Whitlow (1985), Boast (1990), Bullock (1992a) and von der Heyden (2003). The issues at the heart of the debate are the role of the dambo in: (i) the catchment evapotranspiration (ET) budget, (ii) augmentation of dry season flow, (iii) flood flow attenuation and retardation, and (iv) determining the dominant source of water to the dambo and the hydrogeological model.…”

“…The issues at the heart of the debate are the role of the dambo in: (i) the catchment evapotranspiration (ET) budget, (ii) augmentation of dry season flow, (iii) flood flow attenuation and retardation, and (iv) determining the dominant source of water to the dambo and the hydrogeological model. The divergence in the literature regarding these hydrological functions and attributes is shown in Table 1 and in von der Heyden (2003).…”