Total River Flow Research Articles

Study of the glacial flow of rivers in the Grønfjord bay basin (Western Svalbard)

The melting of glaciers in the Arctic archipelagoes provides glacier runoff, which must be considered when assessing river flow. Glacial runoff, as a component of the total river flow, directly affects the thermal and ice conditions of the bays, the productivity and species composition of the marine biota. Also, this process is broadly related to the livelihoods of the Arctic villages. Furthermore, it acts as the important factor for the development of transport and tourism. Melted water of Svalbard glaciers is a significant contribution in total runoff of the local rivers. The issue of this study is to assess this contribution. Grønfjord Bay was selected for assessment because of the fact of regular measurements of water discharge in the river estuaries from June to October. Among 7 rivers flowing into the bay, 6 have glacial runoff. Despite the fact that only small mountain glaciers are common in this area, its melting largely determines the water regime of the rivers. The value of the glacier runoff in Grønfjord Bay was calculated based on an estimation of the glaciers melting by average summer air temperature in 2017 and 2018. Comparison of the amount of glacial and total flow was carried out on the rivers flowing into the Grønfjord Bay.The comparative analysis of the glacial and total river flows size along the 6 rivers of the Grønfjord Bay: Grøndalselva, Grønfjorddalselva, Bretjørna, Aldegonda, Brydebekken, Vasstakelva showed significant differences in the glacier runoff content depending on the area of glaciation in the catchment of rivers. The content of glacial runoff in the total freshwater discharge by rivers into the bay in 2017 and 2018 vary from 20 to 90 %. The largest glacier runoff is observed on the Bretjørna river — 90 %, the Grøndalselva, Brydebekken and Vasstakelva have the smallest glacier runoff — 20 %. The average total glacial runoff of the rivers varied from 41 to 53 % of the total discharge of the rivers of the gulf.

Desiccation events change the microbial response to gradients of wastewater effluent pollution

While wastewater treatment plant (WWTP) effluents have become increasingly recognized as a stressor for receiving rivers, their effects on river microbial communities remain elusive. Moreover, global change is increasing the frequency and duration of desiccation events in river networks, and we ignore how desiccation might influence the response of microbial communities to WWTP effluents. In this study, we evaluated the interaction between desiccation events and WWTP effluents under different dilution capacities. Specifically, we used artificial streams in a replicated regressional design, exposing first a section of the streams to a 7-day desiccation period and then the full stream to different levels of a realistic WWTP effluent dilution, from 0% to 100% of WWTP effluent proportion of the total stream flow. The microbial community response was assessed by means of high-throughput sequencing of 16S rRNA gene amplicons and quantitative PCR targeting ecologically-relevant microbial groups. Threshold Indicator Taxa Analysis (TITAN) was used, together with model fitting, to determine community thresholds and potential indicator taxa. Results show significant interactions between WWTP effluents and desiccation, particularly when sediment type is considered. Indicator taxa included members of Proteobacteria, Actinobacteria and Cyanobacteria, with abrupt changes in community structure at WWTP effluent proportion of the total flow above 50%, which is related to nutrient levels ranging 4.6–5.2 mg N−NO3−L−1, 0.21–0.32 mg P−PO43−L−1 and 7.09–9.00 mg DOC L−1. Our work indicates that situations where WWTP effluents account for >50% of the total river flow might risk of dramatic microbial community structure changes and should be avoided.

Applicability of pressure retarded osmosis power generation technology in Istanbul

In this study, the applicability of pressure retarded osmosis power generation was investigated in order to meet the electricity demand in Turkey. Pressure retarded osmosis (PRO) is a method that converting salinity gradients to power using a semi-permeable membrane against an applied pressure and PRO is one of the promising candidates to reduce fossil fuel dependency. In PRO, water is transported from a low concentrated feed solution to a high-concentrated draw solution. According to the literature findings, in order to produce 1MW of electricity 1m3/s fresh water flow is needed. Turkey is surrounded on three sides by water and has a big potential to develop this technology. Riva River is investigated in the scope this study. Currently Turkey’s total installed power capacity reached 85.200 MW at the end of 2017.Calculations of PRO power generation reveals that it is possible to generate 25,45 MW, If using 5% of total river flow.

Distribution of stable isotopes in water from an alpine river in China

AbstractThe Hailuogou River, on the south-eastern edge of the Tibetan Plateau, receives a substantial portion of its flow from meltwater. The stable isotopic composition and water temperature were observed for waters collected from the main stream and selected tributaries. The results indicate that the river water is generally more depleted in 18O and 2H than groundwater, but more enriched than meltwater. The river water in the upper reaches is characterised by more negative isotopic values, the isotopic fingerprint of meltwaters, and lower temperatures. Both δ18O and δ2H increase significantly during passage from the upper basin downward, at least partly due to enrichment from tributary-inputs. There are also an altitude δ18O-effect of −0.1‰ per 100-m rise, and an altitude δ2H-effect of −0.8‰ per 100-m rise, along the main stream. The positive correlation between isotopic composition and water temperature further highlights the role of meltwater in regulating the river's isotope hydrology. The fraction of meltwater inputs over the total river flow ranges from 67% at Section 11 to 89% at Section 7, in the proglacial headwater region. The tributary-input enrichments and ice-snow melting are the main mechanisms controlling the isotopic composition of river runoff, but depending strongly on altitude.

Use of geochemical tracers for estimating groundwater influxes to the Big Sioux River, eastern South Dakota, USA

Understanding the spatial distribution and variability of geochemical tracers is crucial for estimating groundwater influxes into a river and can contribute to better future water management strategies. Because of the much higher radon (222Rn) activities in groundwater compared to river water, 222Rn was used as the main tracer to estimate groundwater influxes to river discharge over a 323-km distance of the Big Sioux River, eastern South Dakota, USA; these influx estimates were compared to the estimates using Cl− concentrations. In the reaches overall, groundwater influxes using the 222Rn activity approach ranged between 0.3 and 6.4 m3/m/day (mean 1.8 m3/m/day) and the cumulative groundwater influx estimated during the study period was 3,982–146,594 m3/day (mean 40,568 m3/day), accounting for 0.2–41.9% (mean 12.5%) of the total river flow rate. The mean groundwater influx derived using the 222Rn activity approach was lower than that calculated based on Cl− concentration (35.6 m3/m/day) for most of the reaches. Based on the Cl− approach, groundwater accounted for 37.3% of the total river flow rate. The difference between the method estimates may be associated with minimal differences between groundwater and river Cl− concentrations. These assessments will provide a better understanding of estimates used for the allocation of water resources to sustain agricultural productivity in the basin. However, a more detailed sampling program is necessary for accurate influx estimation, and also to understand the influence of seasonal variation on groundwater influxes into the basin.

The impact of water-intake for a tributary on the flow and saline intrusion in the lower Han River

The instream flow of the Ara River is to be supplied from the Han River, and so an Environmental Fluid Dynamics Code (EFDC) model was applied to investigate the impact of water-intake to the Ara River on the total river flow and saline water intrusion. Through the numerical simulation of flow and saline water intrusion under different drainage conditions, it was found that the water intake for the Ara River has an impact not only on the hydraulic characteristics (water level and flow rate), but also on the extent of saline water intrusion in the Han River. It was also found that the change of discharge in the Han River, caused by the water supplying to the Ara River, can increase the salt concentration in the vicinity of the Singok Submerged Weir by 0.5 psu. As agricultural productivity can be affected by even this small amount of salt concentration change, much closer attention should be paid to the relation between water-intake condition and its effect on the Han River.

Impact of Climate Change on the Snow Hydrology of Koshi River Basin

Koshi river basin which is one of the largest river basins of Nepal has its headwaters in the northern Himalayan region of the country covered with perennial snow and glaciers. Increased warming due to climate change is most likely to impact snowpack of this Himalayan region. Snowmelt Runoff Model, a degree day based method, was used in this study to assess the snowmelt hydrology of the five sub-basins, viz. Tamor, Arun, Dudhkoshi, Tamakoshi and Sunkoshi of the Koshi river basin, with and without climate change impacts. The model has been fairly able to simulate the flow. Daily bias-corrected RCM data of PRECIS-ECHAM05 and PRECIS-HadCM3 for the period of 2041-2060 were used for future projection. A period of 2000-2008 was set as baseline period to evaluate changes in future flow. In climate change scenarios, magnitude and frequency of peak flows are expected to increase and snowmelt contribution to total river flows are likely to be more. Simulated flow results indicate that the annual flow would still be governed by monsoon flow even in the future under the climate change impact. A high probability of having more flows and snowmelt in 50’s decade than that in 40’s decade is seen. The estimated future flow by ECHAM05 is found more than those estimated by HadCM3 both seasonally and annually.Journal of Hydrology and Meteorology, Vol. 9(1) 2015, p.28-44

VARIATION OF RIVER FLOW TO CASPIAN SEA FROM THE TERRITORY OF AZERBAIJAN REPUBLIC

During the period 1991–2010 the annual flow of the Kura River at its mouth (Salyan) had decreased by 50% or 13.4 km 3 compared to its many years average value. During this period annual flow of main tributary of Kura, the Aras River at its mouth (Saatli) had decreased by 54% or 4.95 km 3 . Significant reduction of the monthly flow of Kura River also was observed during 1980–2010. Main reason of reduction of flow of these rivers is the increase of water abstraction level and modern climate changes in region. Total river flow to the Caspian Sea from the territory of Azerbaijan during 1991–2010 together with water flow entering through the acting collector drainage network in average makes 18.7 km 3 annually. Consequently total reduction of the river flow to the Caspian Sea mak es 12.2 km 3 annually.

Physically Based Mountain Hydrological Modeling Using Reanalysis Data in Patagonia

Abstract A physically based hydrological model for the upper Baker River basin (UBRB) in Patagonia was developed using the modular Cold Regions Hydrological Model (CRHM) in order to better understand the processes that drive the hydrological response of one of the largest rivers in this region. The model includes a full suite of blowing snow, intercepted snow, and energy balance snowmelt modules that can be used to describe the hydrology of this cold region. Within this watershed, snowfall, wind speed, and radiation are not measured; there are no high-elevation weather stations; and existing weather stations are sparsely distributed. The impact of atmospheric data from ECMWF interim reanalysis (ERA-Interim) and Climate Forecast System Reanalysis (CFSR) on improving model performance by enhancing the representation of forcing variables was evaluated. CRHM parameters were assigned for local physiographic and vegetation characteristics based on satellite land cover classification, a digital elevation model, and parameter transfer from cold region environments in western Canada. It was found that observed precipitation has almost no predictive power [Nash–Sutcliffe coefficient (NS) < 0.3] when used to force the hydrologic model, whereas model performance using any of the reanalysis products—after bias correction—was acceptable with very little calibration (NS > 0.7). The modeled water balance shows that snowfall amounts to about 28% of the total precipitation and that 26% of total river flow stems from snowmelt. Evapotranspiration losses account for 7.2% of total precipitation, whereas sublimation and canopy interception losses represent about 1%. The soil component is the dominant modulator of runoff, with infiltration contributing as much as 73.7% to total basin outflow.

Using 222Rn to identify and quantify groundwater inflows to the Mundo River (SE Spain)

Groundwater discharge to the Mundo River (SE, Spain) has been investigated from 2011 to 2013 by means of 222Rn activities in river water and groundwater. Starting nearby the river source, some 50km of river channel have been studied. The Mundo River is located in the water stressed region of the Segura River Basin. Identifying and quantifying groundwater discharge to rivers is essential for the Hydrological Plan of the Segura Basin Authority. Four main areas of groundwater discharge to the river have been identified by means of 222Rn. Moreover, groundwater fluxes have been quantified using radon activities and, when possible, have been validated with chloride mass balances. The uncertainty range (±2σ) of all water balances has also been assessed. Groundwater discharge (QGW) values estimated by radon mass balances (RMB) and chloride mass balances (CMB) were similar in the river tracts and/or dates in which surface inputs from tributaries were null or negligible. This adds confidence to the QGW values estimated by RMB in the reaches were CMB could not be performed due to the existence of ungauged surface inputs, as is the case of the upper basin of the Mundo River, as well as to the applicability of the method to similar situations. Quantification of groundwater discharge allowed identifying Ayna zone as the main gaining reach of the studied area, with up to 29,553±8667m3day−1 in year 2011. Overall, the total QGW estimated by means of RMB for the studied area was 8–16% of the total river flow. The results are coherent with the meteorological conditions of the study period (average rainfall around 450mm/y) and also with the undisturbed situation of the aquifers discharging to the Mundo River in the considered area.

Incorporation of the Flow Duration Curve Method Within Digital Filtering Algorithms to Estimate the Base Flow Contribution to Total Runoff

The urgent need for rational use of water resources and the intense competition among most of the riparian countries with respect to the use of shared water sources have raised the importance of examining the contribution of base flow to total stream flow. This paper examines the Diyala transboundary river basin shared between Iraq and Iran. Daily unregulated flow records during the hydrologic years between 1955 and 1982 were considered at the upstream flow gauging station and daily unimpaired flow time series during the water years between 1931 and 1961 were examined at the most downstream hydrometric station. Two digital filtering algorithms and the flow duration curve method were applied to extract the base flow time series and compute its signature to total river flow. A generic methodology, which incorporates the flow duration curve method within digital filtering algorithms, has been introduced to obtain the filter parameter α in the filtering algorithms, and obtain the base flow contribution with a high level of confidence. Findings revealed that the base flow proportion is 38 % for the upper sub-basin and 31 % for the upper and middle combined sub-basins. The computed base flow signatures using the incorporated approach have very strong correlation coefficients of around 0.985. The driest year had the highest annual base flow index. The base flow index values started to increase in April and climbed to a peak by the end of May. A gradual decline between August and September was observed. The proposed methodology should be applied to unregulated watersheds.

Hydrologic response of a high altitude glacierized basin in the central Tibetan Plateau

Hydrologic cycles of most high altitude glacierized watersheds in the Tibetan Plateau are not closely monitored due to their inaccessibility. Understanding the hydrologic cycle in such a basin may provide insight into the role climate plays on changes in glacier mass. Thus, hydrologic simulations with a physical perspective in the Tibetan glacierized watershed are of great significance. A high altitude glacierized basin in the central Tibetan Plateau, Qugaqie basin, was investigated with an energy-balance based glacier-melt model and the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. With these two models, glacier mass balance was estimated and basin runoff from glaciers was simulated at a daily time step. Results from the simulation period (October 1, 2006–September 30, 2011) demonstrated that the glaciers experienced a large negative surface mass balance with the cumulative value of −300cmw.e.. In other words, up to 13.93×106m3 water volume was melting out from the glaciers during these five years. In the 2007/08year, however, the glaciers experienced a surplus mass balance because of the low air temperature and increased precipitation in the summer season. Infiltration, evapotranspiration (ET), and overland flow were also calculated using the GSSHA model. Results showed that precipitation, the main water source, contributed roughly 95% to the total mass gain of the annual water balance in the Qugaqie basin during the study period, while the glacial runoff (snow/ice melting) contributed 5% water balance. In the water loss, 17% of annual water volume was consumed by the ET process. As a result, the remaining water volume (83%) converted to the basin river flow to the Lake Nam Co. In the summertime, the glacial runoff accounted for 15% of the total basin runoff volume, while this contribution increased in the upstream portion to 46% due to a large percentage of glacierized area. The analysis showed that the glacial runoff contributions to the total river flow decrease significantly due to the decreased air temperature in the summer of 2008. In general, the integrated model produced acceptable estimations of hydrologic response in this high altitude glacierized basin, which is jointly fed by precipitation and glacial runoff. This study suggests that, a process-based model for glacierized basins can provide a reasonable simulation of hydrologic response and further enhance our understanding of this high altitude region in the Tibetan Plateau.

Alteration of Runoff on the Territory of Moscow as a Result of Landscape Transformations

This paper attempts to assess the runoff alterations on the territory of contemporary Moscow over the past 150 years under the influence of landscape transformations (without taking into account water work facilities transformations, diversions of runoff, water intake and waste water discharge) in the case of average many-year climatic conditions. The landscape dynamics has been tracked. The surface runoff alterations have been reflected. Runoff alterations of infiltration origin and total river flow alterations have been assessed. Particular attention has been paid to the urbanized areas’hydrological role.

Assessment of spatio-temporal variation in larval abundance of lake sturgeon (Acipenser fulvescens ) in the Rupert River (Quebec, Canada), using drift nets

Summary The Rupert River is one of the largest tributaries on the east coast of James Bay. Lake sturgeon (Acipenser fulvescens) is present all along the main stem where several spawning grounds have been located, four of which are major spawning grounds that have been studied at km 216, 281, 290 and 362. The total number of drifting larvae was estimated with drift nets set along transverse transects at km 212, 276, and km 287 from 2007 to 2009, and at km 361 in 2008 and 2009, using a new technique, namely, a Doppler current meter to measure water velocity within transect sub-sections corresponding to Voronoi polygons. There was a substantial, persistent difference in the number of larvae produced by the four main spawning areas. On average, the most productive site (km 276) produced over five times more larvae than the least productive site (km 361). Average estimated numbers were 41,194 at km 212, 176,840 at km 276, 106,212 at km 287, and 30,642 at km 361. Temporal variations were of much less amplitude than spatial differences. Between 2007 and 2009, interannual variations were not significant, except at km 212, despite differences in river flow during incubation and larval drift. The number of gravid females and the quality of spawning grounds would likely be the main factors influencing the total number of larvae. Vertical distribution of larvae is variable between sites and years, and shows a slight tendency for larvae to be more surface oriented. Higher flow near the surface would partly explain larger surface drifting of larvae. Transverse distribution is uneven and often associated with the location of the spawning grounds and the river flow. Given the uneven vertical and transverse distribution of larvae, an effective sampling strategy should cover the complete water column and full river width. Where depth exceeds 3 m, at least two stacked nets are recommended. In large rivers, filtering close to 1% of total river flow should result in acceptable confidence intervals, allowing a good comparison of the number of larvae in space and time.

The stress response of three-spined sticklebacks is modified in proportion to effluent exposure downstream of wastewater treatment works

This study was conducted to investigate whether exposure to wastewater treatment works (WWTW) effluent affects the adaptive stress axis of fish resident within the receiving water. Three-spined sticklebacks (Gasterosteus aculeatus) were sampled from sites downstream of ten WWTWs in north-west England, selected to represent a range of human population equivalents between 1000 and 125,000. Following capture, indices of stress (whole-body cortisol and glucose concentrations) were measured both prior to, and following, the imposition of a standardised stressor to establish both baseline and stress-induced concentrations of cortisol and glucose. There was considerable between-site variation in size, and to a lesser extent condition, of the fish. Pre- and post-stress cortisol and glucose concentrations also varied significantly between-sites. A large proportion of the variation in both the somatic data and the stress response was explained by variation in the proportion of effluent contributing to total river flow at the study sites. Mass (r2=0.35, P<0.001) and length (r2=0.37, P<0.001) of the fish, and cortisol (r2=0.26, P<0.001) and glucose (r2=0.12, P<0.01) concentrations in unstressed sticklebacks, were positively related to the concentration of effluent across the sample sites. However, in stressed fish, cortisol (r2=0.32, P<0.001) and glucose (r2=0.14, P<0.001) concentrations exhibited a negative trend in relation to the effluent concentrations across sites. Individual variation in fish size did not account for the variation in either cortisol or glucose levels. These data provide the first indication that modulation of the stress axis in fish by anthropogenic factors might be widespread and of greater significance than hitherto assumed.

Incorporating land-use changes and surface–groundwater interactions in a simple catchment water yield model

Pressure on limited water resources and the environment requires better understanding of how landscape change impacts river flow. Rainfall-runoff models have traditionally focused on estimating total river flows with less emphasis on modelling the groundwater component or the consequences of different land-use change scenarios. In this paper, we present the GWlag model, a water-generation model that predicts river flows with explicit accounting of the impacts of catchment land-use change and surface–groundwater interactions. The paper firstly describes the theory that underpins the model and its calibration then presents a case study application in the Tarcutta Creek catchment of the Murray–Darling Basin, Australia. The case study aims at: (i) demonstrating the ability of the model to predict daily river flows; (ii) modelling the impacts of hypothetical plantation forestry expansions on river flows; and (iii) showing the impacts of reduced recharge on the low-flow regime using three indices, namely, Q90/Q50 (where Qn refers to nth percentile flow), slope of low-flow part of flow duration curve, and % of zero-flow days. Results showed that predicted flows agreed favourably to those observed at the gauge especially during low-flow conditions. The hypothetical plantation expansion from 32% to 87% of the catchment area has resulted in reductions of 48% and 32%, in Q50 and Q20, respectively. The low-flow indices demonstrated the great sensitivity of low flow to reductions in recharge with the trend of the low-flow response changing to non-linear for recharge reductions beyond 10%. GWlag daily river flow predictions compared favourably to those obtained from four other rainfall-runoff models in terms of the Nash–Sutcliffe model efficiency (E). However, GWlag produced the highest E-value for log-transformed flows thus highlighting the model's superior predictive capability during low-flow conditions.

Defining parameters for Eckhardt's digital baseflow filter

AbstractDigital filters are useful tools for assessing the contribution of groundwater to total river flow. Several of those filters have been proposed in the last decades. One of the last contributions on this subject was given by Ekchardt (2005) who proposed a more general form of a digital baseflow filter and showed that some of the most used filters are special cases of this general form. This new filter has the inconvenience of having two parameters, one of them may be obtained directly from recession analysis, but the other (maximum baseflow index (BFImax)) is routinely estimated by a priori defined values according to the predominant geological characteristics of the drainage basin. In this short communication, we propose a method to estimate BFImax by a backwards filtering operation. The method was applied using data from 15 gauging stations in Brazil, with a varied range of groundwater contribution to streamflow. Results of the new estimation method for the BFImax parameter are coherent with the values which would be adopted by considering geological characteristics of the river basins. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Downriver Passage of Juvenile Blueback Herring near an Ultrasonic Field in the Mohawk River

At the Crescent Hydroelectric Project (Crescent), New York, the Mohawk River is impounded by two dams separated by an island, which creates two channels; the turbine channel conveys water to the hydroelectric turbines, and the main channel conveys water around the turbines. Our objective was to determine whether ultrasound could be used to divert juvenile blueback herring Alosa aestivalis from entering the turbine channel during their fall downriver migration. Fixed-location hydroacoustics (420 kHz) was used to continuously monitor fish passage in the main channel upriver and downriver of the 122–128-kHz ultrasonic projectors. A relative index of abundance was derived from echo integration of acoustic backscatter collected from three horizontally aimed single-beam transducers sampling across each channel, while the proportion and speed of fish moving downriver were estimated from upward-facing split-beam transducers. The presence of juvenile blueback herring was verified by castnetting. Fish migrated downriver episodically for periods of hours rather than days. The mean daily number of downstream migrants (Nd) in the main channel was estimated to be 4.2 times higher at the upriver site than at the downriver site. The estimate for Nd at the main-channel downriver site (NDM) was compared with the expected Nd (NEDM) based on the proportion of total river flow moving through the main-channel downriver site as measured by acoustic Doppler current profilers. The mean daily difference between NDM and NEDM was significantly different from zero. The estimated proportion of fish that passed the main-channel downriver site (31.3%) was almost three times greater than the proportion expected (11.5%). If it is valid to assume that water flow directly influences entrainment and impingement, then the significantly higher-than-expected number of blueback herring that migrated downriver in the main channel could be an indication that ultrasound at Crescent was partially effective in diverting fish. Received July 17, 2011; accepted February 2, 2012

The Karun River waters in the Ambal ridge region (Zagros mountain Range, southwestern Iran): mixing calculation and hydrogeological implications

The Karun River is one of the most important waterways in Iran and the quality level of its waters is very important for all the communities living around it. The salinity of river waters increases and the water quality decreases while it passes through the four km long valley consist of Gachsaran geological formation (mainly gypsum and halit), in the Ambal ridge area. This ridge is located some 5 km upstream of the Gotvand dam (under construction), which in the future will be inundated. In this section of the river, water chemistry suddenly evolves from Ca-HCO3 type with TDS of ~0.4 g/l to Na(Ca)-Cl(SO4) type with TDS of ~1.5 g/l, possibly due to mixing, carbonates precipitation and dolomitization. These variations suggest that saline water mixed with the river water extensively in the Ambal ridge area. Two hypotheses are suggested for the origin of the saline waters: first, in situ dissolution of halite and gypsum units of exposed Gachsaran Formation of the nearby area could produce saline ground-water flow into the river, and second, the intrusion of Karun River water itself through fractures of evaporite layers at location, where it first comes in contact with the Ambal area and in consequence, dissolution of halite and gypsum by the water, which discharge into the river via a number of exposed and underwater springs in the ridge. Calculations indicate that the average annual saline water seepage required for the change of the chemical composition is ~0.24% of the total river flow rate. Water balance calculations suggest that the required catchment area for the saline ground-water flow should be >300 km2, much larger than the Ambal area itself. However, this excess area almost is exist in a closed by plain, the impermeable marl layers in the Gachsaran Formation restraint the flow of groundwater and suggest that the first hypothesis is less likely.

Critical Flow for Water Management in a Shallow Tidal River Based on Estuarine Residence Time

To support the development of protective water resources management strategies, a 3D hydrodynamic model was applied to the Little Manatee River (LMR) to evaluate the effects of reducing river flow and drought on the Estuarine Residence Time (ERT). ERT is an important indicator for estuarine environmental quality. The Little Manatee River is a small tidal river estuary with a yearly mean gaged freshwater inflow of 4.8 m3/s. The hydrodynamic model was calibrated and verified by using two continuous data sets for a six month period. Model simulations were conducted for 17 river inflow scenarios. Among the flow scenarios, 13 scenarios were within a flow range from 0.26 m3/s to 10 m3/s total freshwater inflow. A regression equation (R 2 = 0.98) fitted by a power-law function was derived from analysis of the hydrodynamic modeling results to correlate model predicted ERT to total river inflow, though ERT can be predicted from gaged freshwater inflow as well. The study indicates that the estuarine residence time reaches 53.3 days under an extreme drought condition of 0.26 m3/s total inflow. When river inflow falls below the critical flow (4 m3/s or less), further flow reductions can cause the substantial increases of ERT by a factor of 2 to 10 times. This suggests that the management of flow reductions is particularly critical when total river flows are 4 m3/s or less if adverse impacts to the water quality and ecological characteristics of the Little Manatee River are to be avoided.