Dynamic Flow Alteration Index for Complex River Networks With Cascading Reservoir Systems

Abstract

The natural flow regime of a river is defined by the characteristic pattern of the streamflow variability (Poff et al., 1997). The natural flow regime impacts the riverine habitat, biodiversity, water quality, and overall river ecosystem health (Poff et al., 1997). The alteration of the flow regime is a major factor in degrading the river ecosystem (Poff et al., 2010). The flow regime may change due to human intervention through dams, barrages, land-use and land-cover changes, and changes in the region's hydroclimatology. The world's rivers are regulated through an estimated 2.8 million dams (Lehner et al., 2011) for meeting various human needs such as municipal water supply, flood control, irrigation water supply, and recreational uses. Such regulations alter streamflow in various time scales-hydropeaking alters flow at hourly time scales whereas low flow augmentation affects summer flows, and inter-basin transfers impact the flows over long-term (annual and beyond) (Alonso et al., 2017;Bunn & Arthington, 2002;Stanford & Ward, 1979). The various kinds of flow regulation introduced by these dams have adverse ecological consequences (Poff et al., 1997) as they fragment aquatic habitats (Nilsson et al., 2005) and hinder the movement of species, nutrients, and sediments along the stream (Lehner et al., 2011). Furthermore, such alteration affects the river regime in multiple forms by propagating through river networks multiple ways such as by destabilizing channel morphology (Graf, 2006), by altering the composition and dynamics of aquatic biota (Poff et al., 2007), and by reducing sediment transport (Lehner et al., 2011).Reservoir regulation has been studied over many decades (

How Does Flow Alteration Propagate Across a Large, Highly Regulated Basin? Dam Attributes, Network Context, and Implications for Biodiversity

“…While the Upper Basin uses about half of its 7.5-million-acre fit allocation, demand in the Lower Basin grew hit its full apportionment by the late 1990s (Butler et al, 2021). The fact that most flow is accounted for, and the high degree of regulation and water residence time of the large dams in the lower Colorado main-stem (Kumar et al, 2022), likely decreases R 2 values by temporally decoupling inputs and outputs at each reservoir. This may take place if water is released to fulfill downstream needs when inputs during that particular month do not increase; or if inputs at the reservoir level are diverted or used, and are thus not reflected as outputs (leading to a temporal decoupling or asynchrony, and hence a low Figure 6.…”

Improved National‐Scale Above‐Normal Flow Prediction for Gauged and Ungauged Basins Using a Spatio‐Temporal Hierarchical Model

“…Since streamflow is regulated by reservoirs to meet downstream water demand (Kumar et al., 2022), we consider cumulative upstream reservoir storage of a USGS gaging station as a predictor in the hierarchical model. Studies have shown that reservoir storage and their retention time significantly alter the downstream flow characteristics (Chalise et al., 2021).…”

Improved National-Scale Flood Prediction for Gauged and Ungauged Basins using a Spatio-temporal Hierarchical Model

“…Since streamflow is regulated by reservoirs to meet downstream water demand (Kumar et al, 2022), we consider cumulative upstream reservoir storage of a USGS gaging station as a predictor in the hierarchical model. Studies have shown that reservoir storage and their retention time significantly alter the downstream flow characteristics (Chalise et al, 2021).…”