An investigation of flows and losses within the alluvial sands of ephemeral rivers in Zimbabwe

Mansell, M. G.; Hussey, Stephen W.

doi:10.1016/j.jhydrol.2005.03.015

Cited by 39 publications

(54 citation statements)

References 8 publications

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“…The beds of sand rivers form alluvial aquifers: unconfined, horizontally semi-continuous layers of sand, silt and clay forming the river channel, banks and, in places, flood plains. Because of the aquifers' shallow depth and intimate relationship with the river, flow in alluvial aquifers is essentially an extension of surface flow (Mansell and Hussey, 2005). Recharge of these aquifers is continuous for perennial rivers, but the more common case is annual recharge from an ephemeral river (Barker and Molle, 2004).…”

Section: The Potential Of Alluvial Aquifers In Ephemeral Riversmentioning

confidence: 99%

A water balance modelling approach to optimising the use of water resources in ephemeral sand rivers

Love¹,

Zaag

Uhlenbrook

et al. 2011

River Research & Apps

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Alluvial aquifers present a possibility for conjunctive use with surface reservoirs for the storage of water in ephemeral sand rivers such as the Mzingwane River in the Limpopo Basin, Zimbabwe. The Lower Mzingwane valley is a semi-arid region with high water stress, where livelihoods have revolved around the large rivers for thousands of years. However, current water allocation favours the commercial user: of the 2600 ha irrigated in the 5960 km 2 (596 000 ha) region, only 410 ha are for smallholder farmers. A water balance approach was used to model the surface water resources and groundwater resources to determine the potential for expanding irrigation and to explore water allocation options. Using a combination of field and laboratory investigations, remote sensing and existing data, the Lower Mzingwane valley was modelled successfully using the spreadsheet-based model WAFLEX, with a new module incorporated to compute the water balance of alluvial aquifer blocks.Results showed that the Lower Mzingwane alluvial aquifers can store 38 Â 10 6 m 3 of water, most of that storage being beyond the reach of evaporation. Current water usage can be more than tripled: the catchment could supply water for currently-planned irrigation schemes (an additional 1250 ha), and the further irrigation of two strips of land along each bank of the Mzingwane River (an extra 3630 ha)-without construction of any new reservoirs. The system of irrigating strips of land along each bank of the Mzingwane River would be decentralized, farmer or family owned and operated and the benefits would have the potential to reach a much larger proportion of the population than is currently served. However, there could be substantial downstream impact, with around nearly onethird of inflows not being released to the Limpopo River.The approach developed in this paper can be applied to evaluate the potential of alluvial aquifers, which are widespread in many parts of semi-arid Africa, for providing distributed access to shallow groundwater in an efficient way. This can enhance local livelihoods and regional food security.

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Section: The Potential Of Alluvial Aquifers In Ephemeral Riversmentioning

confidence: 99%

A water balance modelling approach to optimising the use of water resources in ephemeral sand rivers

Love¹,

Zaag

Uhlenbrook

et al. 2011

River Research & Apps

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show abstract

“…In Southern Africa, groundwater from alluvial aquifers located along both ephemeral and perennial rivers is used to meet agricultural and domestic requirements [1]. Ephemeral rivers are more common in Southern Africa due to extended periods (>9 months) without significant rainfall events [2]. During these dry periods farmers rely heavily on groundwater.…”

Section: Introductionmentioning

confidence: 99%

“…Secondly, over abstraction from the aquifer causing an increase in the ingress from the river bed and finally the dewatering of the alluvial aquifer can negatively affect the riparian vegetation [5]. Most of these problems that can arise in alluvial aquifers require a good understanding on the spatial variation of physical geological properties of the system, since these factors have a considerable influence on the groundwater flow and transport processes.A number of hydrogeological studies have been conducted on alluvial channel aquifer in Southern Africa [2,[6][7][8]. Most of the studies have focused on assessment of the potential yield and sustainability of the aquifer with no effort being devoted to the spatial variation of geological aquifer materials and their influence on hydrogeological properties.…”

Section: Introductionmentioning

confidence: 99%

Development of a Preliminary Hydrogeology Conceptual Model for a Heterogeneous Alluvial Aquifer using Geological Characterization

Tonder¹

2013

J Geol Geosci

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Geological characterization of a heterogeneous alluvial channel aquifer was conducted using outcrop mapping and analysis of lithological logs from 15 boreholes drilled at the site. The study was aimed at developing a preliminary hydrogeology conceptual model. A total of 12 lithological samples were tested in the laboratory using falling head permeameter to determine the hydraulic conductivity of each unconsolidated lithology unit. Shale and calcrete outcrops were observed on the study site. Outcrop mapping on the site also indicated the presence of a contact plane between the overlying unconsolidated sediments and the shale of the underlying bedrock where a groundwater discharge zone has been created. Geology logs show that the alluvial channel aquifer comprises of three distinct layered unconsolidated sediment materials (calcrete, clay-silt, sand-gravel deposited formations) that overlie low permeable shale formation. Geological lithology revealed the spatial variation in the nature and type of unconsolidated sediments deposits between boreholes that can influence groundwater occurrence and flow in the aquifer system. The gravel-sand aquifer layer that consists of medium to large pebbles is conceptually the main hydraulically conductive unit with an average laboratory determined hydraulic conductivity of 8.5 m/day. Hydraulic gradient calculated using a combination of boreholes ranges from 0.013-0.022.

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“…These measures are (i) heightening the spillway of the 'Mnyabezi 27' dam and (ii) constructing a sand storage dam in the alluvial aquifer of the Mnyabezi River. Sand storage dams store water in the alluvial sediments, which are accumulated upstream of the dam (Hanson, 1987;Mansell and Hussey, 2005). The sediment becomes saturated after a river flow event.…”

Section: Introductionmentioning

confidence: 99%

Potential water supply of a small reservoir and alluvial aquifer system in southern Zimbabwe

Hamer

Love²,

Owen

et al. 2008

Physics and Chemistry of the Earth, Parts A/B/C

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Groundwater use by accessing alluvial aquifers of non-perennial rivers can be an important additional water resource in the semi-arid region of southern Zimbabwe. The research objective of the study was to calculate the potential water supply for the upper-Mnyabezi catchment under current conditions and after implementation of two storage capacity measures. These measures are heightening the spillway of the 'Mnyabezi 27' dam and constructing a sand storage dam in the alluvial aquifer of the Mnyabezi River. water resource, because the storage capacity of the alluvial aquifer is small. However, when an ephemeral river is underlain by a larger alluvial aquifer, a sand storage dam is a promising way of water supply for smallholder farmers in southern Zimbabwe.

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An investigation of flows and losses within the alluvial sands of ephemeral rivers in Zimbabwe

Cited by 39 publications

References 8 publications

A water balance modelling approach to optimising the use of water resources in ephemeral sand rivers

A water balance modelling approach to optimising the use of water resources in ephemeral sand rivers

Development of a Preliminary Hydrogeology Conceptual Model for a Heterogeneous Alluvial Aquifer using Geological Characterization

Potential water supply of a small reservoir and alluvial aquifer system in southern Zimbabwe

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