Salt transport on islands in the Okavango Delta: Numerical investigations

Zimmermann, Stephanie; Bauer, Péter; Held, Rudolf; Kinzelbach, Wolfgang; Walther, Jens Honoré

doi:10.1016/j.advwatres.2005.04.013

Cited by 64 publications

(45 citation statements)

References 23 publications

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“…The use of fully coupled groundwater flow and salinity transport modelling in relation to wetland and river ecology has only recently commenced (e.g. Langevin et al, 2005;Bauer et al, 2006a,b;Zimmermann et al, 2006). These numerical models are extremely complex and require large amounts of data to parameterize reliably, and so they are unlikely to see widespread management use.…”

Section: Wetland Gw-sw Modellingmentioning

confidence: 98%

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

2008

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In arid/semi-arid environments, where rainfall is seasonal, highly variable and significantly less than the evaporation rate, groundwater discharge can be a major component of the water and salt balance of a wetland, and hence a major determinant of wetland ecology. Under natural conditions, wetlands in arid/semi-arid zones occasionally experience periods of higher salinity as a consequence of the high evaporative conditions and the variability of inflows which provide dilution and flushing of the stored salt. However, due to the impacts of human population pressure and the associated changes in land use, surface water regulation, and water resource depletion, wetlands in arid/semi-arid environments are now often experiencing extended periods of high salinity. This article reviews the current knowledge of the role that groundwater-surface water (GW-SW) interactions play in the ecology of arid/semi-arid wetlands. The key findings of the review are as follows:1. GW-SW interactions in wetlands are highly dynamic, both temporally and spatially. Groundwater that is low in salinity has a beneficial impact on wetland ecology which can be diminished in dry periods when groundwater levels, and hence, inflows to wetlands are reduced or even cease. Conversely, if groundwater is saline, and inflows increase due to raised groundwater levels caused by factors such as land use change and river regulation, then this may have a detrimental impact on the ecology of a wetland and its surrounding areas. 2. GW-SW interactions in wetlands are mostly controlled by factors such as differences in head between the wetland surface water and groundwater, the local geomorphology of the wetland (in particular, the texture and chemistry of the wetland bed and banks), and the wetland and groundwater flow geometry. The GW-SW regime can be broadly classified into three types of flow regimes: (i) recharge-wetland loses surface water to the underlying aquifer; (ii) discharge-wetland gains water from the underlying aquifer; or (iii) flow-through-wetland gains water from the groundwater in some locations and loses it in others. However, it is important to note that individual wetlands may temporally change from one type to another depending on how the surface water levels in the wetland and the underlying groundwater levels change over time in response to climate, land use, and management. 3. The salinity in wetlands of arid/semi-arid environments will vary naturally due to high evaporative conditions, sporadic rainfall, groundwater inflows, and freshening after rains or floods. However, wetlands are often at particular risk of secondary salinity because their generally lower elevation in the landscape exposes them to increased saline groundwater inflows caused by rising water tables. Terminal wetlands are potentially at higher risk than flow-through systems as there is no salt removal mechanism. 4. Secondary salinity can impact on wetland biota through changes in both salinity and water regime, which result from the hydrological and hydrogeo...

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Section: Wetland Gw-sw Modellingmentioning

confidence: 98%

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

2008

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“…[2] The simulation of buoyancy driven flow (BDF) is frequently required in many areas of hydrology including saline contamination [Zimmermann et al, 2006;Bolster et al, 2007;Narayan et al, 2007;Lin et al, 2009] and more recently carbon sequestration [Riaz et al, 2006;Farajzadeh et al, 2007;Hassanzadeh et al, 2007]. A major issue in BDF modeling is the problem of benchmarking [Simpson and Clement, 2003;Simmons, 2005;Goswami and Clement, 2007].…”

Section: Introductionmentioning

confidence: 99%

Insights from a pseudospectral approach to the Elder problem

Reeuwijk

Mathias

Simmons

et al. 2009

Water Resources Research

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[1] The aim of this paper is to clarify and circumvent the issue of multiple steady state solutions in the Elder problem. A pseudospectral method is used to avoid numerical error associated with spatial discretization. The pseudospectral method is verified by comparison to an analytical solution at Rayleigh number, Ra = 0, and by reproducing the three stable steady state solutions that are known to exist at Ra = 400. A bifurcation diagram for 0 < Ra < 400, which is free of discretization error, confirms that multiple steady states are indeed an intrinsic characteristic of the Elder problem. The existence of multiple steady states makes the Ra = 400 Elder problem less suitable for benchmarking numerical models. To avoid the multiple steady states, we propose a benchmark at Ra = 60. The results for this Low Rayleigh Number Elder Problem are presented and compared to simulations with the commercial groundwater modeling package FEFLOW. Correspondence between the pseudospectral model and FEFLOW is excellent.

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“…The fundamental concept of the SEAWAT model is to combine the two commonly used groundwater flow and solute transport modeling programs, MODFLOW (Anderson and Woessner 1992;Harbaugh and McDonald 1996) and MT3DMS (Zheng and Wang 1999;Zheng and Bennett 2002) into a single program that solves the density-dependent groundwater flow and solute transport equations. The governing equation for densitydependent groundwater flow in terms of freshwater head as represented in MODFLOW routines and SEAWAT is well described by Andersen et al (1988), Zheng and Bennett (2002), Langevin et al (2003), Bakker et al (2004), Zimmermann et al (2006), and Lin et al (2009).…”

Section: Seawat Modelingmentioning

confidence: 98%

Assessment of possibility of saltwater intrusion in the central Godavari delta region, Southern India

Surinaidu¹,

Rao

Jampani³

et al. 2014

Reg Environ Change

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Oil exploration and development have taken place extensively in the near-shore waters of the Bay of Bengal for over two decades, with onshore coastal aquifers serving as a primary source of water injected into nearshore production wells for enhanced oil recovery. Field and modeling studies were initiated to assess the effects of potential seawater intrusion into the coastal aquifers and to improve strategies for groundwater development and management. Groundwater levels were measured at 42 locations in the central Godavari delta (295 km 2 ) over a period of 2 years (2006)(2007). These data indicated that the predominant groundwater flow direction consistently points toward the coast with no significant change in groundwater table elevations during the study period. Groundwater samples analyzed for major ions revealed the groundwater to be brackish in nature with an average salinity of *5,000 mg L -1 . A numerical model of variable density, groundwater flow, and solute transport (SEA-WAT) was developed for the study region. After calibrating against observed hydraulic head data for the year 2006 at steady state, the model was used to predict the extent of seawater intrusion in the study area over the next 50 years. The estimated regional groundwater budget indicates a significant amount of groundwater outfall to the Bay of Bengal. The model predicts that the area will not be affected by seawater intrusion at the present rate of groundwater exploitation near the coast.

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Salt transport on islands in the Okavango Delta: Numerical investigations

Cited by 64 publications

References 23 publications

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

Insights from a pseudospectral approach to the Elder problem

Assessment of possibility of saltwater intrusion in the central Godavari delta region, Southern India

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