Shoreline erosion: a cautionary note in using small farm dams to determine catchment erosion rates

Lloyd, Sara Dorothy; Bishop, Paul; Reinfelds, Ivars

doi:10.1002/(sici)1096-9837(199810)23:10<905::aid-esp910>3.0.co;2-e

Cited by 18 publications

(10 citation statements)

References 12 publications

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“…2d) worsen gully erosion in the study area. Similar observations are reported in other regions (e.g., Trimble and Mendel, 1995;Lloyd et al, 1998).…”

Section: Correlation Analysismentioning

confidence: 99%

Analysis of factors determining sediment yield variability in the highlands of northern Ethiopia

et al. 2006

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“…2d) worsen gully erosion in the study area. Similar observations are reported in other regions (e.g., Trimble and Mendel, 1995;Lloyd et al, 1998).…”

Section: Correlation Analysismentioning

confidence: 99%

Analysis of factors determining sediment yield variability in the highlands of northern Ethiopia

et al. 2006

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“…Brune (1953) already noticed that his TE estimation approach that relies on MAR values might lead to an overestimation of the TE for intermittently dry reservoirs. Borland, 1971;Lloyd et al, 1998;Verstraeten and Poesen, 2000). Borland, 1971;Lloyd et al, 1998;Verstraeten and Poesen, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…Depending on their design and operation, high net evaporation loss and intermittent inflow may lead to prolonged periods without outflow (Haregeweyn et al, 2006), while storm events might result in spillage significantly contributing to the overall sediment discharge (Faithful and Griffiths, 2000). So far, little effort has been made to investigate the appropriateness of established empirical approaches to estimate the TE of small reservoirs with variable and peaked hydrographs (Lloyd et al, 1998). So far, little effort has been made to investigate the appropriateness of established empirical approaches to estimate the TE of small reservoirs with variable and peaked hydrographs (Lloyd et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Lewis et al (2013) demonstrated that the TE of the large Burdekin Falls Dam (storage capacity: 1.9 × 10 9 m 3 ), located in the tropical summer rainfall zone of northeast Australia, was overestimated by the standard Brune and Churchill equations and that estimates could be improved by considering daily discharge rather than annual or long-term mean inflow. So far, little effort has been made to investigate the appropriateness of established empirical approaches to estimate the TE of small reservoirs with variable and peaked hydrographs (Lloyd et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Estimating the sediment trap efficiency of intermittently dry reservoirs: lessons from the Kruger National Park, South Africa

Reinwarth

Riddell

Glotzbach

et al. 2017

Earth Surf Processes Landf

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The assessment of sediment yield from reservoir siltation requires knowledge of the reservoir's sediment trap efficiency (TE). Widely used approaches for the estimation of the long‐term mean TE rely on the ratio of the reservoir's storage capacity (C) to its catchment size (A) or mean annual inflow (I). These approaches have been developed from a limited number of reservoirs (N ≤ 40), most of them located in temperate climate regions. Their general applicability to reservoirs receiving highly variable runoff such as in semi‐arid areas has been questioned. Here, we examine the effect of ephemeral inflow on the TE of 10 small (≤ 280 × 103 m3), intermittently dry reservoirs located in the Kruger National Park. Fieldwork was conducted to determine the storage capacity of the reservoir basins. The frequency and magnitude of spillage events was simulated with the daily time step Pitman rainfall–runoff model. Different runoff scenarios were established to cope with uncertainties arising from the lack of runoff records and imperfect input data. Scenarios for the relationship between water and sediment discharge were created based on sediment rating curves. Taking into account uncertainties in hydrological modelling, uncertainties of mean TE estimates, calculated from all scenarios (N = 9), are moderate, ranging from ±6 to ±11% at the 95% confidence level. By comparison, estimating TE from the storage capacity to catchment area (C/A) ratio induces high uncertainty (ranges of 35 to 65%), but this uncertainty can be confined (15 to 33%) when the latter approach is combined with hydrological modelling. Established methods relying on the storage capacity to mean annual inflow (C/I) ratio most probably lead to an overestimation of the TE for the investigated reservoirs. The approach presented here may be used instead to estimate the TE of small, intermittently dry reservoirs in semi‐arid climate regions. Copyright © 2017 John Wiley & Sons, Ltd.

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“…commn.). Stock or farm ponds for cattle or agricultural purposes are also numerous, e.g., in Australia where in a 2000 ha catchment 242 farm dams were reported (Lloyd et al, 1998) and, in a 13 600 ha catchment, 330 farm dams (Neil and Mazari, 1993), or in southern Zambia where at least 537 small dams had been constructed by 1991 (Sichingabula, 1997). In Italy, it is estimated that there are more than 8000 dams with a mean capacity of 30 000 m 3 , mainly for water supply to agriculture but also for industrial and civic use (Bazoffi et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Estimating trap efficiency of small reservoirs and ponds: methods and implications for the assessment of sediment yield

Verstraeten

Poesen

2000

Progress in Physical Geography: Earth and Environment

263

107

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Throughout the world, several millions of small ponds exist for water supply, irrigation, flood control or to control water quality downstream. The reduced flow velocity in these ponds causes sedimentation of tranported particles. For most ponds this is a negative impact as their retention capacity decreases due to sedimentation processes. Sediment volumes in small ponds can be used to reconstruct sediment yield values and to study the spatial variation in sediment yield over large areas. Especially in developing countries, this technique can be very helpful in establishing large data sets on sediment delivery as there are often no resources for expensive monitoring programmes. However, when such studies are undertaken, one has to take into account the efficiency of the pond in trapping sediments. This trap efficiency is dependent on the characteristics of the inflowing sediment and the retention time of the water in the pond, which in turn are controlled by pond geometry and runoff characteristics. Because trap efficiency is one of the most important properties of a pond or reservoir, it has been studied for quite some time. This article provides an overview of the different methods available to estimate the trap efficiency of reservoirs and ponds. The first set of methods are empirical models that predict trap efficiency, mostly of normally ponded large reservoirs using data on a mid to long-term basis. These models relate trap efficiency to a capacity/watershed ratio, a capacity/annual inflow ratio or a sedimentation index. Today, these models are the most widely used models to predict trap efficiency, even for reservoirs or ponds that have totally different characteristics from the reservoirs used in these models. For small ponds, these models seem to be less appropriate. They also cannot be used for predicting trap efficiency for a single event. To overcome these restrictions, different theoretical models have been developed based on sedimentation principles. These can be very simple, such as the overflow rate method, but also very complex when runoff and sediment are routed through a pond with incremental time-steps. The theoretical-based models are probably more capable of predicting trap efficiency for small ponds with varying geometric characteristics, and some of them also provide data on effluent sediment concentrations and quality. However, when reconstructing sediment yield values using sedimentation rates over a period of a few months to a few year (the mid-term basis), one needs a trap efficiency value for the whole period, not for one single event. At present only limited research has been done on establishing mid-term trap efficiency models based on theoretical principles. This is probably the most important gap in trap efficiency research.

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Shoreline erosion: a cautionary note in using small farm dams to determine catchment erosion rates

Cited by 18 publications

References 12 publications

Analysis of factors determining sediment yield variability in the highlands of northern Ethiopia

Analysis of factors determining sediment yield variability in the highlands of northern Ethiopia

Estimating the sediment trap efficiency of intermittently dry reservoirs: lessons from the Kruger National Park, South Africa

Estimating trap efficiency of small reservoirs and ponds: methods and implications for the assessment of sediment yield

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