A study of wetland hydrology and ecosystem service provision: GaMampa wetland, South Africa

Abstract

The GaMampa wetland, a palustrine wetland, comprises less than 1% of the catchment but is widely believed to make a significant contribution to dry-season river flow in the Mohlapitsi River, a tributary of the Olifants River, in South Africa. The contribution of the GaMampa wetland to dry-season flow in the Mohlapitsi River and the impact of increasing agriculture on its hydrological functioning were investigated. Economic analyses showed that the net financial value of the wetland was US$ 83 263 of which agriculture comprises 38%. Hydrological analyses indicated that the Mohlapitsi River contributes, on average, 16% of the dry-season flow in the Olifants River. However, the wetland contributes, at most, 12% to the increase in dry-season flow observed over the reach of the river in which the wetland is located. The remainder of the increase originates from groundwater flowing through the wetland. Furthermore, despite the conversion of 50% of the wetland to agriculture since 2001, there has been no statistically significant reduction in dry-season flow in the Mohlapitsi River. These results highlight the importance of understanding the nature of the full suite of services being provided by a wetland in order to make informed decisions for appropriate management.Key words agriculture; ecosystem services; hydrology; livelihoods; South Africa; wetland Une étude de l'hydrologie et de la fourniture de services écosystémiques des zones humides: la zone humide de GaMampa, Afrique du Sud Résumé La zone humide de GaMampa, une zone humide palustre, représente moins de 1% du bassin versant auquel elle appartient, mais il est communément admis qu'elle apporte en saison sèche une contribution significative au débit de la rivière Mohlapitsi, affluent de la rivière Olifants, en Afrique du Sud. Nous avons étudié la contribution de la zone humide de GaMampa au débit de la rivière Mohlapitsi en saison sèche et l'impact croissant de l'agriculture sur son fonctionnement hydrologique. Les analyses économiques ont montré que la valeur financière nette de la zone humide était de 83 263 US$ dont 38% correspondent à l'agriculture. Les analyses hydrologiques ont montré que la rivière Mohlapitsi contribue en moyenne pour 16% au débit de la rivière Olifants en saison séche. Cependant, la zone humide contribue à 12% au plus de l'augmentation du débit observé en saison séche sur la portion de la rivière sur laquelle la zone humide est située. Le reste de l'augmentation provient de l'eau souterraine qui coule au travers de la zone humide. Par ailleurs, malgré la conversion de 50% de la zones humide en terres agricoles depuis 2001, il n'y a pas eu de réduction statistiquement significative du débit de saison sèche de la rivière Mohlapitsi. Ces résultats soulignent combien il est important de comprendre la nature de la gamme complète de services fournis par une zone humide, afin de prendre des décisions éclairées pour une gestion appropriée.

Impact of Climate and Land Use/Land Cover Change on the Water Resources of a Tropical Inland Valley Catchment in Uganda, East Africa

“…Wetlands cover 30,105 km 2 of Uganda's total land area of 241,500 km 2 , a share of 13% of the total land area [8], representing one of the most vital ecological and economic resources in the country. Wetlands offer numerous ecosystem services and functions ranging from provisioning to regulation and cultural services [9][10][11][12]. However, their integrity in offering ecosystem services and functions are being jeopardized due to factors such as anthropogenic activities, including population growth, degradation of arable upland soils, and increasing unpredictability of precipitation [13,14].…”

Assessment of a judgment‐based hydrogeomorphic wetland classification using long‐term hydrologic data

“…If a site can be correctly classified, and the hydrologic behavior of that classified group can be predicted, then enormous time and effort can be saved in the process. Unfortunately, most wetland hydrologic studies cover only a few years (e.g., Cole et al, 1997;Hunter, Faulkner, & Gibson, 2008;McCartney, Morardet, Rebelo, Finlayson, & Masiyandim, 2011). To my knowledge, no one has continuously measured hydrology and then assessed the veracity of an HGM classification.…”

Managing water and agroecosystems for food security

“…in the Andean páramo), are often regarded as functioning as natural sponges; they expand to accommodate excess water in times of heavy rain and contract as they release water slowly throughout the dry season, thereby maintaining streamfl ow (Millennium Ecosystem Assessment, 2005). In reality, the hydrological functions of most wetlands are more complex and vary considerably among sites (Bullock and Acreman, 2003;McCartney et al, , 2011a. Inland wetlands, in particular, play a major role in providing water for agriculture (Falkenmark et al, 2007).…”

“…Other important benefi ts associated with wetlands include base-fl ow releases during dry seasons, the capacity to provide off-season biomass (fi sh and crops) and their role as biodiversity hotspots -they often provide habitats for nationally or globally threatened species, though once again, the evidence base for all such benefi ts may not be that strong (e.g. McCartney et al, 2011a).…”