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Flood Hydrograph and Baseflow Separation Using the Web- Based Hydrograph Analysis Tool
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Different locations have varying degrees of baseflow contribution to the streamflow based on the regional hydrogeological conditions. These can result in streams gaining (receipt of groundwater flow) and losing (discharge to groundwater system) conditions over time and space. Hence, understanding the local characteristics is imperative for the detailed analysis of baseflow conditions as many of the automated baseflow separation approaches do not distinguish between these physical states. Conceptually, the groundwater–surface water interaction processes are increased during a flood event, with significantly greater volumes both in the river and the surrounding landscape. A flood event causes a fast but temporary increase in stream water level that moves rapidly downstream under the force of gravity. This increase in water level can lead to a change in hydrostatic pressure between the river and the groundwater in the surrounding bank. In a gaining stream, depending on the hydrostatic pressure in the surrounding aquifer, this can stimulate the movement of flow from the stream to the bank. As the flood peak subsides, water moves back to the stream and the hydrostatic pressure in the river reduces. Groundwater discharge from aquifers represents the baseflow contribution to streamflow (Brandes et al., 2005). This occurs when the hydrostatic pressure of groundwater is higher than the stream, when aquifer is regularly recharged, and is made up of materials that support the storage and transmission of flow to the stream (Smakhtin, 2001).
Water sources for flowing water fish culture
Published in Richard W. Soderberg, Aquaculture Technology, 2017
Stream flow consists of runoff, channel precipitation, and base flow, minus water losses to consumption, evaporation, and seepage. Base flow is the contribution to stream discharge from groundwater. The amount of precipitation that runs off a particular watershed is referred to as the hydrologic response and is expressed as a percentage. The hydrologic response is calculated from a hydrograph, which measures direct runoff above base flow following a precipitation event and from rain gauges in the watershed, which measure total precipitation. Hydrologic response values may range from 1% to 75% and are related to soil permeability, bedrock porosity, slope, and vegetation. Mountainous areas with shallow soils and impermeable bedrock have high hydrologic responses because a relatively large fraction of the water that falls as precipitation enters streams. Low hydrologic responses occur in areas where most of the precipitation enters the groundwater due to low gradients, permeable soils, and porous bedrock, such as limestone or shale.
Exposure and sensitivity of other ecosystem services and feedbacks between climate change and land degradation
Published in Mark S. Reed, Lindsay C. Stringer, Land Degradation, Desertification and Climate Change, 2016
Mark S. Reed, Lindsay C. Stringer
Regulating ecosystem services are likely to be exposed and sensitive to a range of potential interactions between climate change and land degradation. Effects of climate change on the regulation of water quality and supplies for agriculture are likely to have a major impact on land degradation processes, leading to land abandonment where it is no longer possible to irrigate crops and water livestock. At the same time, land degradation can contribute towards and exacerbate water quality and supply problems through erosion, which can lead to the sedimentation of dams used for irrigation and the release of nutrients and stored pollutants from historic atmospheric deposition (e.g. heavy metals). Although winter base flow and mean annual stream flow is predicted to increase in most regions under climate change (IPCC, 2013), reduced summer rainfall predicted in some parts of the world may reduce the volume of water in rivers, leading to the concentration of pollutants in stream water to levels that may be toxic for use in agriculture (Confalonieri et al., 2007). The livelihood and wider economic consequences of this for irrigated agricultural systems may be significant, as has been illustrated in the case of the Aral Sea in Central Asia (Box 5.1).
Baseflow index assessment for agriculture-industry led Ramganga river basin
Published in Journal of Applied Water Engineering and Research, 2023
In the monsoon season, the long-term average BFI ranges from 21% to 26% among the three CWC sites. It suggests that surface runoff dominates river discharge throughout the entire basin during this period and may be considered virtually the same for all CWC sites irrespective of the basin area. For the monsoon season, it may also be noted from Table 7 that the percentage increment in the baseflow index for any two CWC sites is equal to the percentage increment in normally distributed rainfall for the respective sites. The normally distributed rainfall is the long-term average rainfall per unit basin area. The correlation in the increment indicates the baseflow is generated through interflow rather than groundwater in the monsoon period. In contrast, in the non-monsoon period, the baseflow is contributed mainly by the groundwater. BFI for the Moradabad-Bareilly basin part is highest in the monsoon season. It may be due to two reasons, (a) the annual average rainfall is higher in the Moradabad-Bareilly basin part compared to other basin parts, consequently higher recharge to the sub-surface, and (b) excess water is released through dams-barrages in tributaries that contain a greater fraction of baseflow.
Testing a modified environmental flows framework for a Southern Ontario (Canada) river system: assessing hydrological alteration and management recommendations
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2021
David Lembcke, Lance Aspden, Mason Marchildon, Steven Murray, Brian K. Ginn
Baseflow is the component of river flow coming from relatively stable sources such as groundwater, wetlands, or lakes and excludes storm event flows (Metcalfe et al. 2013). As the portion of the flow regime that is sustained between precipitation events, maintaining baseflow is essential to healthy ecological functioning in river systems. Brook trout, a key indicator of ecosystem health in coldwater habitats, are positively correlated to baseflow and baseflow index (BFI, the proportion of the total flow volume that is comprised of baseflow volume), as well as forested land cover (Stranko et al. 2008; Thorn, Chu, and Jones 2016). Although modeled baseflow volume showed an increase at Lover’s Creek, BFI decreased with increasing urban land cover, particularly between May and December (Figure 2(b)). The modeled mean annual pre-settlement BFI was 0.74, compared to BFI = 0.71 for the mid-development scenario, and BFI = 0.62 for the current condition. The decrease in BFI between the pre-settlement and mid-development scenarios was not statistically significant.
Benefits and limitations of using isotope-derived groundwater travel times and major ion chemistry to validate a regional groundwater flow model: example from the Centre-du-Québec region, Canada
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2018
Sylvain Gagné, Marie Larocque, Daniele L. Pinti, Marion Saby, Guillaume Meyzonnat, Pauline Méjean
Baseflow data are usually obtained by hydrograph separation using algorithms that make use of the total flow rate time series (e.g. Chapman 1991; Arnold & Allen 1995; Eckhardt 2005). It is generally recognized that these methods tend to overestimate baseflows, especially during high-flow periods, such as spring snowmelt or storm events (Croteau et al. 2010; Rivard et al. 2014). Manual stream flow measurements during low-flow periods are also an effective way to estimate river baseflows, but values obtained in this way represent a single baseflow measurement, which would need to be repeated at different times to provide a reliable estimate of groundwater discharge to streams and rivers. During the model calibration process, estimated baseflows can be compared to river and stream outflows simulated by the groundwater flow model.