Variations In River Discharge Research Articles

A Holistic Modeling Approach to Project the Evolution of Inlet-Interrupted Coastlines Over the 21st Century

Approximately one quarter of the World’s sandy beaches, most of which are interrupted by tidal inlets, are eroding. Understanding the long-term (50-100 year) evolution of inlet-interrupted coasts in a changing climate is therefore of great importance for coastal zone planners and managers. This study therefore focuses on the development and piloting of an innovative model that can simulate the climate-change driven evolution of inlet-interrupted coasts at 50-100 year time scales, while taking into account the contributions from catchment-estuary-coastal systems in a holistic manner. In this new model, the evolution of inlet-interrupted coasts is determined by: (1) computing the variation of total sediment volume exchange between the inlet-estuary system and its adjacent coast, and (2) distributing the computed sediment volume along the inlet-interrupted coast as a spatially and temporally varying quantity. The exchange volume, as computed here, consists of three major components: variation in fluvial sediment supply; basin (or estuarine) infilling due to the sea-level rise-induced increase in accommodation space; and estuarine sediment volume change due to variations in river discharge. To pilot the model, it is here applied to three different catchment-estuary-coastal systems: the Alsea estuary (Oregon, USA), Dyfi estuary (Wales, UK), and Kalutara inlet (Sri Lanka). Results indicate that all three systems will experience sediment deficits by 2100 (i.e. sediment importing estuaries). However, processes and system characteristics governing the total sediment exchange volume, and thus coastline change, vary markedly among the systems due to differences in geomorphic settings and projected climatic conditions. These results underline the importance of accounting for the different governing processes when assessing the future evolution of inlet-interrupted coastlines.

River discharge variability as the link between climate and fluvial fan formation

AbstractThere are two contrasting hypotheses on whether fluvial fans need specific climate conditions to form. Deduction of climatic and tectonic signals from landscapes and the sedimentary record is a key aim in geology and geomorphology. It is thus of great interest to obtain recognition criteria for specific climate changes in the sedimentary record in general, and fluvial fans in particular, because they may form the bulk of the continental fluvial record. The hypothesis that links fluvial fan occurrence to climate specifically indicates precipitation variability as a key control, because it promotes streamflow variability, channel instability, and avulsions, which are the key processes involved in fluvial fan formation. Here, we tested this hypothesis by quantitative analyses of discharge patterns from 68 fan-forming rivers that have a global distribution. Using an ensemble of dimensionless metrics, we show that 75% of the fan-forming rivers in this data set have a high discharge variability. We further analyzed down-fan changes in discharge variability and discuss the nature of discharge variability in different hydroclimates as a function of intra- and interannual precipitation fluctuations. We also examined the fan-forming rivers with moderate to low discharge variability and concluded that although river discharge variability strongly promotes fluvial fan formation, fluvial fans may also be formed by rivers with a moderate or low discharge variability if other favorable conditions that promote avulsions occur.

Benefits of representing floodplains in a Land Surface Model: Pantanal simulated with ORCHIDEE CMIP6 version

Tropical floodplains have a significant impact on the regional water cycle and on land-atmosphere interaction but are not always considered in Land Surface Models (LSMs) or in Earth system models. This study evaluates the importance of representing tropical floodplains in an LSM to provide realistic river discharges, evapotranspiration fluxes and other variables crucial for land’s interaction with the ocean and atmosphere. Off-line simulations of the world’s largest tropical wetland, the Pantanal are conducted with ORCHIDEE, the LSM of IPSL’s regional and global Earth system model. We analyse the period 1961–2000, which includes both dry and wet decades. Atmospheric uncertainty is considered through the utilization of three forcing data sets, each one in two versions: the original dataset and a regionally bias adjusted version. The activation of the floodplain module leads to a systematic improvement of intra-annual variability and extremes of river discharge. Temporal evolution and spatial distribution of flooded area are coherent with satellite estimations, although the model, due to the coarse resolution of the topography, underestimates the extent of the area. Considering floodplains in ORCHIDEE enhance the evapotranspiration since it permits the water from the upstream region to evaporate in the plains. This have strong consequences on the water balance and on the spatial pattern of surface fluxes. The simulations allow us to perform a model-guided residual estimation of evapotranspiration through a water balance obtaining an annual evapotranspiration over Pantanal of 1220 mm while precipitation is estimated to be 1250 mm with an uncertainty of 180 mm.

Regionalization of stage-discharge rating curves for hydrodynamic modeling in ungauged basins

Stage-discharge rating curves are empirical power functions that represent river dynamics by explaining the temporal variations of river discharge with respect to stage fluctuations. The widespread access to measured river discharge and stage at gauging stations in the United States provides a valuable opportunity to perform regionalization techniques and transfer this information to ungauged areas. In this study, a recently proposed regionalization framework that integrates the behavioral-based hierarchical clustering (BHC) with classification and aggregation, namely BHC-CA, is applied to 128 rating curves in the Arkansas-White-Red region to detect homogeneous river reach catchments with similar river dynamics. Additionally, the performance of the BHC, compared to commonly used attribute-based hierarchical clustering (AHC) algorithms, is tested. The BHC-CA framework divides the entire study area into three homogeneous clusters, creates three regional rating curves and finds a logistic regression with 7 physical/climatic attributes as the best classifier for transferring regional rating curves to ungauged catchments. Results also demonstrate the effectiveness of the BHC and its usefulness as an alternative clustering algorithm for the regionalization of environmental model problems.

Water flow and temperature as main factors that regulate phytoplankton and cyanobacterial blooms in a large subtropical river

Seasonal variations and interannual changes (2006-2019) of the phytoplankton community, related to variations in water quality and river discharge, in the lower part of the Uruguay River in South America are presented. In total, 422 microalgae and cyanobacterial taxa were identified. Cryptophytes, cyanobacteria, and diatoms were the most important groups. Although nanoflagellates and cryptophytes were always present in plankton, statistical differences were found in seasonal assemblages of phytoplankton. According to the similarity analysis (SIMPER), the typical species for each season were identified: Aulacoseira spp. in winter, Dolichospermum uruguayense, Durinskia baltica and Ankistrodesmus arcuatus in spring, Microcystis aeruginosa, M. wesenbergii, Dolichospermum uruguayense and D. circinale in summer and Ceratium cf. furcoides, A. arcuatus, Raphidiopsis and Jaaginema sp. in autumn. Under lentic river conditions (<2000 m3 s-1) and above 22ºC, high biomass was recorded due to the blooms of Microcystis and Dolichospermum. In 2010, M. panniformis reached 10.4 µg l-1 microcystin-LR. Raphidiopsis mediterranea and R. raciborskii began to be registered in Spring (2009 and 2014 respectively) reaching 1041 cell ml-1 in Spring 2017. This paper shows that flow, transparency and temperature are the main factors that regulate phytoplankton biomass and cyanobacterial blooms in the Uruguay River. In the summer, when the Uruguay River is in low flow conditions, cyanobacteria remain in the river. When flow increases, cyanobacteria are transported downstream and could reach the estuary of the Rio de la Plata, impacting its beaches.

Hydro-climatology study of the Ogooué River basin using hydrological modeling and satellite altimetry

Hydrological models are important tools for the simulation of water storage and hydrological fluxes in large basins and complex river systems. The hydrological models can compensate the lack of observed data in ungauged basins. In this study, the hydrological model of large basins MGB (for Model of Large Basins in Portuguese) is used to evaluate the hydrological processes of the Ogooué River Basin (ORB), which has been mostly unmonitored for about three decades. Simulations were carried out over an 18-year period from 1998 to 2015 using TRMM 3B42 daily rainfall data from the Tropical Rainfall Measurement Mission (TRMM) as forcing and in situ and altimetry-based river discharges from Envisat, Saral Altika and Jason-2 for calibration and validation. The results of the model were in good agreement with the flows measured at stations upstream and downstream of the Ogooué basin (Nash-Sutcliffe Efficiency (NSE) > 0.56 for all calibration gauges). The MGB model efficiently describes the seasonal and interannual variations of the flow in the Ogooué River and its major tributaries which were found to be highly correlated to the rainfall (r ranging from 0.72 to 0.90 and 0.56 to 0.87 at seasonal and interannual time-scales respectively). Interannual variations of precipitation and river discharge of the ORB are linked to the El Niño Southern Oscillation (ENSO) in the tropical eastern Pacific Ocean and southeastern tropical Atlantic Niño. Also, the Ogooué River discharge was found to be strongly correlated with Sea Surface Temperature (SST) at annual and semi-annual time-scales.

Intra-catchment comparison and classification of long-term streamflow variability in the Alps using wavelet analysis

Understanding the temporal and spatial variability of river discharge of alpine hydrological systems is of particular interest due to their relevance for water uses including water provisioning, hydropower production and touristic activities. Streamflow variability is highly heterogeneous both in time and space due to several reasons, such as a differentiated response to climate change, differences in catchment morphology and geographic location. Therefore, catchment classification for these systems is challenging. A suitable tool to determine the crucial scales of variability of a non-stationary time series is wavelet transform. In this work, we compute the wavelet coherence between fifty selected gauging stations located within the Inn River catchment to classify them by runoff behavior, focusing only on long term variability, between one and eight years scales. This choice allows us to filter out the effect of local meteorological patterns and the effects of hydropower production. In addition, we decompose the streamflow signals in three levels (256 days, three years, six years) using Discrete Wavelet Transform to further understand the detected alterations in the streamflow signal. Three main runoff behaviors (referred as three classes) are found at the yearly scale. Focusing on two-four years scales a loss of coherence between time series located at different elevations becomes significant in the 1980s. Prior to 1980 we detect four different behaviors, while after 1980 we detect eleven different classes. At larger scales the stations are clustered in four classes. Our analysis highlights that catchment classification may depend on the scale of the analyzed signal and it may vary both in time and space. This research contributes to the development of new methods for catchment classification, which is highly relevant for many hydrological applications such as prediction in ungauged basins, model parameterization, understanding the potential impact of environmental and climatic changes, and transferring information from gauged catchments to the ungauged ones.

Monitoring water discharge and floodplain connectivity for the northern Andes utilizing satellite data: A tool for river planning and science-based decision-making

River discharge data and magnitudes of floods are often not readily available for decision makers of many developing nations, including Colombia. And this while flooding for these regions is often devastating, causing many fatalities and insurmountable damage to the most vulnerable communities. During the wet season, in strong La Niña years, infrastructural damages of over $US 7.2 billion have occurred. Mitigation of such natural disasters lacks data-supported scientific approaches for evaluating river response to extreme climate events. Here, we propose a satellite-based technique to measure river discharge at selected sites for the main northern Andean River, the Magdalena. This method has the advantage of back calculating daily river discharges over a period of two decades, and thus making it possible to calculate return intervals of significant flood events. The study shows that satellite based river discharges well capture a) the inter-annual variability of river discharge; b) the natural seasonality of water discharge along the floodplains; and c) peak discharges that were observed during La Niña conditions between 2008 and 2011. The last is likely more accurate compared to ground-based gauging stations, as ground-based stations tend to overflow during large flood events and as such are hampered to accurately monitor peak discharges. Furthermore, we show that these derived discharges can form the base to study river-floodplain connectivity, providing environmental decision makers with a technique that makes it possible to better monitor river and ecosystem processes.

Assessing the impact of human activities and rainfall variability on the river discharge of Komadugu-Yobe Basin, Lake Chad Area

The impact of human activities and rainfall variability on river discharge is of main concern for policymakers in the Komadugu-Yobe Basin (KYB), Lake Chad area. The KYB is of strategic importance because its rivers contribute significantly to the recharge of Lake Chad whose shrinkage has been of concern to policymakers and the international society. This study investigates the variations in river discharge of the KYB as a result of the contributory effects of rainfall variability and human influences, using daily rainfall and discharge data between 1971 and 2013. In order to partition the impacts of rainfall variability and human activities on river discharge, breakpoints related to abrupt environmental changes caused by human activities are identified using the generalized variance (GV), double mass curve (DMC) and the wavelet spectral methods. Breakpoints are found in 1974 and 1993, which correspond to times when major dams in the basin became operational. These breakpoints may also be related to LULC changes. The land-use land-cover (LULC) analysis shows an increase in bare surface, plantation, settlements and water bodies from 1975 to 2013, in association with a decrease in the forest and grassland coverage. Overall, the mean discharge between the pre-break and post-break periods increased by 24%. This increment in discharge was caused by approximately 50% rainfall variability and 50% human activities. Hence, the effects of human activities appear to be as important as the effect of natural rainfall variability on the river discharge changes in the KYB.

Impact of Flow Alteration and Temperature Variability on Hyporheic Exchange

AbstractCoupled groundwater flow and heat transport within hyporheic zones extensively affect water, energy, and solute exchange with surrounding sediments. The local and cumulative implications of this tightly coupled process strongly depend on characteristics of drivers (i.e., discharge and temperature of the water column) and modulators (i.e., hydraulic and thermal properties of the sediment). With this in mind, we perform a systematic numerical analysis of hyporheic responses to understand how the temporal variability of river discharge and temperature affect flow and heat transport within hyporheic zones. We identify typical time series of river discharge and temperature from gauging stations along the headwater region of Mississippi River Basin, which are characterized by different degrees of flow alteration, to drive a physics‐based model of the hyporheic exchange process. Our modeling results indicate that coupled groundwater flow and heat transport significantly affects the dynamic response of hyporheic zones, resulting in substantial differences in exchange rates and characteristic time scales of hyporheic exchange processes. We also find that the hyporheic zone dampens river temperature fluctuations increasingly with higher frequency of temperature fluctuations. This dampening effect depends on the system transport time scale and characteristics of river discharge and temperature variability. Furthermore, our results reveal that the flow alteration reduces the potential of hyporheic zones to act as a temperature buffer and hinders denitrification within hyporheic zones. These results have significant implications for understanding the drivers of local variability in hyporheic exchange and the implications for the development of thermal refugia and ecosystem functioning in hyporheic zones.

Effects of Dam Regulation on the Hydrological Alteration and Morphological Evolution of the Volta River Delta

The Volta River in West Africa is one of the most regulated rivers influenced by dams in the world, and the regulation has resulted in substantial impacts on the hydrological alteration and morphological evolution of the Volta River Delta. However, comprehensive analyses of the relevant effects are still lacking to date. In this study, inter-annual variations of river discharge and sediment load for pre- and post-Akosombo Dam periods (1936 to 2018) were analyzed through simple regression and Mann–Kendall (MK) trend analysis whereas the intra-annual variations were dictated by the non-uniformity and regulated coefficients. The shoreline changes were further evaluated using Landsat remote sensing images (1972 to 2018) to explore the effects of hydrological alteration on the morphological evolution of the Volta River Delta. Hydrological analyses show that the inter- and intra-annual variations are much higher in the pre-dam period, suggesting the substantial regulation of the Akosombo Dam on the Volta River. The dam regulation has more significant effects on the sediment load delivered to the delta than the river discharge, which decreased by 92.32% and 23.23%, respectively. Morphological analyses show that the progradation-erosion of the Volta River Delta constantly fluctuates within a relatively small range (maximum 0.5%) after the 1970s. The relationship between the variations of the delta area and sediment load implicates that a quasi-equilibrium state may have been established at the Volta River Delta, given the current sediment load. Our findings provide references for the future regulation and restoration of the Volta River Delta.

Terrestrial Signature in Coral Ba/Ca, δ18O, and δ13C Records From a Macrotide‐Dominated Nearshore Reef Environment, Kimberley Region of Northwestern Australia

AbstractThe geochemistry preserved in massive scleractinian corals has long been used as proxies for river runoff, but its reliability in naturally extreme environment (i.e., strong hydrodynamics and intensive thermal stress) has not been tested yet. Using Porites coral collected from the macrotidal nearshore Kimberley region of northwestern Australia, we assess the impacts of river runoff and associated changes in this extreme environment using elemental (Ba/Ca) and isotopic (δ18O and δ13C) compositions at both near monthly and annual resolutions. On the monthly timescales, significant terrestrial signatures were noted in skeletal Ba/Ca, ∆δ18O, and to a lesser extent in δ13C time series, highlighting their linkage to runoff input of Fitzroy River. However, all the geochemical time series as well as the observational coastal sea surface salinity exhibited a consistent ~1‐ to 2‐month lag with river discharge, possibly a manifestation of the sluggish water and sediments exchange in King Sound which are likely induced by strong tidal forcing. On the annual timescales, Ba/Ca follows the variation in river discharge, while freshwater supplied by both runoff and rainfall all contributed to δ18O variations. In contrast, annual δ13C is mainly dominated by the 13C Suess effect, showing a gradually downward trend. Importantly, we find that δ18O and Ba/Ca records exhibit consistent and significant long‐term trends, with δ18O being decreasing and Ba/Ca being increasing, coupled with the increased Australian monsoon, indicating that strengthened monsoon precipitation has likely brought more freshwater and sediment loads to the nearshore Kimberley region.

Estuarine Exchange Flow Variability in a Seasonal, Segmented Estuary

AbstractSmall estuaries in Mediterranean climates display pronounced salinity variability at seasonal and event time scales. Here, we use a hydrodynamic model of the Coos Estuary, Oregon, to examine the seasonal variability of the salinity dynamics and estuarine exchange flow. The exchange flow is primarily driven by tidal processes, varying with the spring–neap cycle rather than discharge or the salinity gradient. The salinity distribution is rarely in equilibrium with discharge conditions because during the wet season the response time scale is longer than discharge events, while during low flow it is longer than the entire dry season. Consequently, the salt field is rarely fully adjusted to the forcing and common power-law relations between the salinity intrusion and discharge do not apply. Further complicating the salinity dynamics is the estuarine geometry that consists of multiple branching channel segments with distinct freshwater sources. These channel segments act as subestuaries that import both higher- and lower-salinity water and export intermediate salinities. Throughout the estuary, tidal dispersion scales with tidal velocity squared, and likely includes jet–sink flow at the mouth, lateral shear dispersion, and tidal trapping in branching channel segments inside the estuary. While the estuarine inflow is strongly correlated with tidal amplitude, the outflow, stratification, and total mixing in the estuary are dependent on the seasonal variation in river discharge, which is similar to estuaries that are dominated by subtidal exchange flow.

Beyond the trends: The need to understand multiannual dynamics in aquatic ecosystems

Beyond the trends: The need to understand multiannual dynamics in aquatic ecosystems

Hydrological processes interconnecting the two largest watersheds of South America from seasonal to intra‐monthly time scales: A critical review

AbstractMany articles on the subjects of moisture transport, precipitation and surface hydrology of the two largest watersheds of South America, the Amazon and the La Plata basins, are stitched together to obtain an overview of the aspects related to the hydrological processes interconnecting them on time scales ranging from seasonal to intra‐monthly. In the mean, moisture from the tropical Atlantic Ocean is transported by the trade winds into the Amazon Basin. A good part of it precipitates over the Amazon Basin and the other part reaches the La Plata Basin by northerly winds east of the Andes. Besides the moisture transported from the Atlantic, there is evapotranspiration in the Amazon and La Plata basins. A part of the evapotranspiration of the Amazon Basin precipitates over the same basin, contributing with about 1/3 of annual precipitation this basin, and a part joins the aerial stream into the La Plata Basin, contributing with about 1/4 of its annual precipitation. Semi‐permanent and transient meteorological systems such as Inter‐Tropical Convergence Zone, South Atlantic Convergence Zone, Low‐Level Jet (LLJ) east of the Andes, Madden–Julian Oscillation, cold fronts and cyclones play an important role in the seasonal and intra‐seasonal variations of precipitation, evapotranspiration and river discharge. The hydrological memory in Amazonian soils and the LLJ constitute an inter‐seasonal coupling between the water balances of the two basins. All these aspects are succinctly described and discussed in this review article. Hypotheses for future research are formulated.

Impact of trends in river discharge and ocean tides on water level dynamics in the Pearl River Delta

The spectrum of tidal and subtidal water level variations in river deltas responds to river discharge variation, ocean tides, and human activities of many kinds. It remains a contemporary challenge to identify the main sources of changes in tidal dynamics in deltas, because of nonlinear interactions between tides and the river discharge in a changing setting. Understanding the main forcing factors controlling the evolution of mean water levels and the associated amplitudes and phases of tidal constituents can help to understand the causes of floods and the occurrence of low flows hindering navigation. Here, a nonstationary harmonic analysis tool (NS_TIDE) is applied to hydrological data from 14 stations in the Pearl River Delta (PRD) spanning the period 1961–2012. The water levels and main tidal constituent properties are decomposed into contributions of external forcing by river discharges and ocean tides, providing insight into the nonstationary tidal-fluvial processes. Significant temporal trends in mean water levels and tidal properties are observed in the PRD. Results indicate that there is spatial variability in the response of mean water levels and tidal properties to river discharge variation in the delta. The abrupt changes in bathymetry in the delta due to intensive sand excavation are likely responsible for the observed spatial variations in tidal response, which reduce the flood-dominant tidal asymmetry in this area.

Numerical investigation of the spatial distribution ofEscherichia coliin river deltas for different values of river discharge, temperature and irradiation of the water surface

AbstractEscherichia coli and other enteric pathogens' presence indicate that the water has been contaminated with fecal matter. River deltas are population hotspots which are becoming increasingly urbanized and where poor sanitation has been frequently identified as a pressing issue. In this study, we have investigated the spatial distribution of E. coli in river deltas under varying river discharge, temperature and irradiation at the water surface. A hydrodynamic and water quality model has been used to reproduce an idealized river delta configuration and to investigate the spatial distribution of E. coli across the delta floodplain and channels. The concentration of E. coli rapidly declines downstream, following a tripartite trend with different decline rates on the delta front, pro-delta and shelf area. The highest differences in the spatial distribution of E. coli bacteria occur for low-river discharge values. Temperature and irradiation both influence the concentration of E. coli and mostly influence downstream areas and smaller channels.

Monitoring hydropower reliability in Malawi with satellite data and machine learning

Hydro-climatic extremes can affect the reliability of electricity supply, in particular in countries that depend greatly on hydropower or cooling water and have a limited adaptive capacity. Assessments of the vulnerability of the power sector and of the impact of extreme events are thus crucial for decision-makers, and yet often they are severely constrained by data scarcity. Here, we introduce and validate an energy-climate-water framework linking remotely-sensed data from multiple satellite missions and instruments (TOPEX/POSEIDON. OSTM/Jason, VIIRS, MODIS, TMPA, AMSR-E) and field observations. The platform exploits random forests regression algorithms to mitigate data scarcity and predict river discharge variability when ungauged. The validated predictions are used to assess the impact of hydroclimatic extremes on hydropower reliability and on the final use of electricity in urban areas proxied by nighttime light radiance variation. We apply the framework to the case of Malawi for the periods 2000–2018 and 2012–2018 for hydrology and power, respectively. Our results highlight the significant impact of hydro-climatic variability and dry extremes on both the supply of electricity and its final use. We thus show that a modelling framework based on open-access data from satellites, machine learning algorithms, and regression analysis can mitigate data scarcity and improve the understanding of vulnerabilities. The proposed approach can support long-term infrastructure development monitoring and identify vulnerable populations, in particular under a changing climate.

Evaluation of MAR Methods for Semi-Arid, Cold Regions

Mongolia is a semi-arid, highly continental region with highly variable precipitation and river discharge. The groundwater aquifer located near Ulaanbaatar, the capital city of Mongolia, is the only one source for city water supply consumption, and it is important to ensure that groundwater is available now and in the future. The main watercourse near the capital city is the Tuul River, fed by precipitation in the Khentii Mountains. The semi-arid and cold environment shows high variability in precipitation and river discharge. However, due to absence of precipitation in winter and spring, the riverbed usually runs dry during these times of the year, and weather observations show that the dry period has been extending in recent years. However, in parallel with urban development, the extended groundwater aquifer has shown a clear decline, and the groundwater levels have dropped significantly. Therefore, a groundwater management system based on managed aquifer recharge is proposed, and a strategy to implement these measures in the Tuul River valley is presented in this paper. This strategy consists of the enhancement of natural recharge rates during the wet summer from the northern drainage canal, an additional increase in groundwater recharge through melting the ice storage in the dry period, as well as the construction of underground dams to accumulate groundwater and a surface water reservoir that releases a constant discharge in the outlet. To increase natural recharge rates of groundwater during the early dry period through the melting ice storage period, the MATLAB icing code, which was written for ice storage for limited and unlimited areas, was considered through finite element subsurface FLOW (FEFLOW) simulation scenarios as a water source in ice form on the surface. A study of the artificial permafrost of underground as an ice dam was processed in FEFLOW simulation scenarios for accumulating groundwater resources. The results of these artificial recharging methods were individually calculated, combined, and compared with the surface reservoir, which releases a constant discharge through the dam. In this paper, new ideas are presented involving managed aquifer recharge—MAR methods, and include application to aufeis, a mass of layered ice for groundwater recharge by melting. Additionally, the accumulation of groundwater using artificial permafrost is used as an underground dam. In addition, was considered recharging scenario only with constant release water amount from water reservoir also with all MAR methods together with reservoir combination.

Using ichnological relationships to interpret heterolithic fabrics in fluvio‐tidal settings

AbstractIn fluvio‐tidal settings, the sediment is dominantly derived from the river systems. However, the importance of landward tidal transport of sediment in tidally influenced sedimentary environments is difficult to assess, particularly in the rock record. This problem is addressed using two intervals within the Lower Cretaceous McMurray Formation, each representing a distinct inclined heterolithic stratification motif. The ichnological variation between the heterolithic intervals is analyzed to determine which lithosomes are associated with brackish‐water (tidally influenced) colonization windows. From this, the relative fluvial influence responsible for the deposition of the fine and coarse members can be determined. Both of the inclined heterolithic stratification fabrics studied record the deposition of fluvio‐tidal point bars wherein the heterolithic bedding represents variations in river discharge. The first fabric comprises inclined heterolithic stratification in which bioturbation only occurs in mudstone beds. This fabric indicates that deposition occurred in more proximal positions within a fluvio‐tidal system (i.e. the outermost inner to middle estuary or distributary channels). In this example sand deposition is interpreted to represent high‐energy, freshwater dune migration within a fluvial‐dominated setting, whereas mud beds reflect brackish‐water suspension deposition during times of low river discharge. The second fabric, which is interpreted to have developed in more distal depositional positions (i.e. the middle estuary or seaward of the turbidity maximum in deltas), consists of inclined heterolithic stratification with laminated mudstone and bioturbated sandstone. In these inclined heterolithic stratification successions the mudstone beds were deposited under the influence of freshwater and heightened sedimentation rates, whereas bioturbated sandstone was colonized under brackish‐water conditions and in the presence of tidally facilitated sediment transport. In both examples, the bioturbated lithosomes are related to colonization windows that indicate the predominance at that time of marine or tidally influenced processes over fluvial processes.