Surface Water Flow Research Articles

Modeling of Border Irrigation in Soils with the Presence of a Shallow Water Table. I: The Advance Phase

The overelevation of the water table in surface irrigation plots is one of the main factors affecting salinization in agricultural soils. Therefore, it is necessary to develop simulation models that consider the effect of a shallow water table in the process of advance-infiltration of the water in an irrigation event. This paper, the first in a series of three, develops a simple mathematical model for the advance phase of border irrigation in soils with the presence of a shallow water table. In this study, the hydrodynamic model of the Barré de Saint-Venant equations is used for the water surface flow, and the equations are solved using a Lagrangian finite-differences scheme, while in the subsurface flow, an analytical solution for infiltration in soils with a shallow water table is found using the bisection method to search for roots. In addition, a hydraulic resistance law is used that eliminates the numerical instabilities presented by the Manning–Strickler law. The model results for difference irrigation tests show adjustments with an R2 > 0.98 for the cases presented. It is also revealed that, when increasing the time step, the precision is maintained, and it is possible to reduce the computation time by up to 99.45%. Finally, the model proposed here is recommended for studying the advance process during surface irrigation in soils with shallow water tables.

РОЗРОБЛЕННЯ ТА УДОСКОНАЛЕННЯ МЕТОДІВ РОЗРАХУНКУ ДЕФОРМАЦІЇ НЕРЕГУЛЯРНИХ РУСЛОВИХ ФОРМ ТА ОСНОВ РІЧКОВИХ СПОРУД ПІД ДІЄЮ ПОВЕНЕВИХ ТЕЧІЙ

Abstract Introduction. The article presents the results of the study of irregular bottom river forms and foundations of structures, as well as coastal forms under the action of surface channel currents. It is assumed that the development of channels occurs due to the action of natural hydromorphodynamic river processes during the long stages of rivers existence formed in accordance with topographic, geological and hydrometeorological conditions. Problem Statement. Flow velocities are determined by a system of equations for the kinematics of channel flows and sediment transport, which is built on the basis of averaging the depth of flow. Purpose. Application of the developed methods of solving problems in the spatial dimension for the study of turbulent effects in the interaction with structural elements. The development of methods for applying the spatial model will be carried out at the next stage. Methods of research. Differential equations describing a nonstationary depth-averaged flow are solved using the FST2DH numerical model, which implements the finite element method. The steps typically performed when using FST2DH to study surface water flow and sediment transportation require the general necessary geographic information systems to build a network and assign boundary conditions. The equations for calculating channel erosion and erosion of bridge piers in bound soils are also considered, where it is shown that erosion depends more on soil properties than for the case of incoherent sediments, but can reach the same erosion depths with longer multi-flood calculations hydrographs. Results. Calculations of the flow kinematics of the calculated floodplain on the example of crossing the floodplain along the highway showed that the presence of a large angle of the overpass to the flood flow leads to additional conditions for increasing local erosion of supports in the form of solid rectangular columns. Significant local erosion is observed in the area of supports near the channel part. Conclusion. Based on the calculations and analysis of the kinematics and hydromorphodynamics of flows in the area of the designed bridge, recommendations on the necessary layout and design protective measures have been developed. Keywords: channel processes, erosion of bound and unbound bottom soils, erosion of piers bases of bridge crossings and overpasses, numerical methods.

Таац голын усны горимын судалгаа

Surface water resources and flow regime of the river are dependent on climate, physical geography, soil condition, geology and hydrogeological conditions of the basin. These factors vary spatially and temporally and affect the runoff. To study the flow regime of the river including snowmelt and rainfall flow is crucial information for flood mitigation, control, water harvesting, hydro construction planning, dam and other hydrologic systems, etc. Therefore, we attempted to investigate the flow regime and its changes of the Taats river which is located in the Asian internal drainage basin in this study. The study was conducted using the daily runoff, precipitation and air temperature data for the period of 1975-2019. In addition, the Mann-Kendall test was applied to detect trend analysis for the annual runoff and maximum flow of the snowmelt and rainfall events. The probability of the maximum runoff of the snowmelt was estimated through the Gringorten method. The results show that the mean annual runoff and snowmelt flow decreased and rainfall flow has increased insignificantly in the study period. However, it was observed the changes in the timing of the snowmelt runoff shifted toward later in the year 1975-1990, earlier in the year 1991-2003 and on average in the period of 2004-2019. The maximum runoff of the snowmelt and rainfall is estimated at 13.2 m3/s and 275 м3/c, respectively in the 100 years.

Estimating Soil Surface Roughness With Models Based on the Information About Tillage Practises and Soil Parameters

AbstractThe quantitative description of the soil surface roughness is necessary for effective monitoring of wind, water and tillage erosion, hydrological processes or greenhouse gas emissions. The aim of this work was to build soil roughness predictive models based on the type of tillage tool, the roughness indices and soil properties. The roughness formed by five tillage tools was determined. Two surface roughness indices: Height Standard Deviation (HSD) and T3D (Tortuosity index) were calculated from Digital Elevation Model. The both roughness indices demonstrated a significant correlation, however, they provided different information about soil roughness. The HSD describes roughness on the “macro,” while T3D refers to the “micro” scale. Hence, our findings show that a single index is not sufficient to describe the roughness of post‐treatment surface. The linear and random forest models were built to describe the relationships between the roughness indices, type of tillage tool and soil properties. The HSD analysis indicated that the type of tillage tools had the greatest impact on post‐treatment roughness. In contrast, T3D analysis found soil texture to have a significant effect, together with tillage tools. In all modeling scenarios, T3D was more accurately predicted than HSD by both the linear (R2 = 0.62 vs. R2 = 0.60) and random forest models (R2 = 0.58 vs. R2 = 0.55). Predictive soil surface roughness models can be applied effectively for estimating water retention in soil, the intensity and speed of surface water flow, soil erosion, the level of reflected shortwave solar radiation or soil properties by remote sensing techniques.

Steady vs dynamic stream-aquifer interactions: Lower Flint River Basin, Southwest Georgia, USA

Study regionThe Lower Flint River Basin (LFRB): a karst catchment in southwestern Georgia, USA. Study focusA year-long field campaign from July 2018 to July 2019 measured steady and dynamic stream-aquifer exchanges on Ichawaynochaway Creek (INC), a fifth-order tributary to the karstic Flint River in Georgia. The net change in discharge along a 24-km Creek segment was determined between two US Geological Survey gaging stations with no surface-water inflows. Stream-aquifer interactions were measured along a 120-m piezometer transect perpendicular to the bank. Hydraulic parameters to aid future modeling efforts were estimated using the method of moments applied to changes in bank flow direction from Hurricane Michael. New hydrological insights for the regionResults display the effects of local water use on streamflow as most channel storage gains occurred in the fall and winter. Negligible net channel gains and some losses occurred during the spring and summer months. Approximately 150 million m3 of net channel gains were observed during the study period. Initial stormflow contributed to aquifer recharge as indicated by reversals in the hydraulic gradient. Diffusivity and transmissivity increased along the transect (9–420 m2/d) and (3–150 m2/d), respectively, and hydraulic conductivity equaled 2.85 m/d. Stream-reach orientation with respect to regional groundwater gradients explains increased stream-aquifer interactions. Surface-groundwater interactions in karst systems are better understood after characterizing variation of hydraulic processes.

Organizational Principles of Hyporheic Exchange Flow and Biogeochemical Cycling in River Networks Across Scales

AbstractHyporheic zones increase freshwater ecosystem resilience to hydrological extremes and global environmental change. However, current conceptualizations of hyporheic exchange, residence time distributions, and the associated biogeochemical cycling in streambed sediments do not always accurately explain the hydrological and biogeochemical complexity observed in streams and rivers. Specifically, existing conceptual models insufficiently represent the coupled transport and reactivity along groundwater and surface water flow paths, the role of autochthonous organic matter in streambed biogeochemical functioning, and the feedbacks between surface‐subsurface ecological processes, both within and across spatial and temporal scales. While simplified approaches to these issues are justifiable and necessary for transferability, the exclusion of important hyporheic processes from our conceptualizations can lead to erroneous conclusions and inadequate understanding and management of interconnected surface water and groundwater environments. This is particularly true at the landscape scale, where the organizational principles of spatio‐temporal dynamics of hyporheic exchange flow (HEF) and biogeochemical processes remain largely uncharacterized. This article seeks to identify the most important drivers and controls of HEF and biogeochemical cycling based on a comprehensive synthesis of findings from a wide range of river systems. We use these observations to test current paradigms and conceptual models, discussing the interactions of local‐to‐regional hydrological, geomorphological, and ecological controls of hyporheic zone functioning. This improved conceptualization of the landscape organizational principles of drivers of HEF and biogeochemical processes from reach to catchment scales will inform future river research directions and watershed management strategies.

Effective treatment of acid mine drainage using a combination of MgO-nanoparticles and a series of constructed wetlands planted with Vetiveria zizanioides: A hybrid and stepwise approach

In this novel study, acid mine drainage (AMD) was treated using a hybrid approach comprising a nano-and-biotic system synergistically integrated in a step-wise and modular fashion. Specifically, the treatment chains were made up of different stages, which comprise, neutralization using activated magnesite or MgO-nanoparticles (NPs) (Stage 1) and polishing the product water using a series of wetlands (Stage 2) in a step-wise connection. In stage One (1), real AMD was treated with MgO-NPs at a ratio of 1:100 (1 g/100 mL - w/v ratio), 500 rpm of mixing speed, and One (1) hour of hydraulic retention time (HRT) whilst in stage 2, the final water was fed into constructed wetlands, i.e. Three (3) interconnected wetland with different flow modalities [(I) subsurface vertical flow (SSVF-CW), (II) free water surface flow (FWS-CW), and (III) subsurface horizontal flow (SSHF-CW)], for further purification and polishing to the desired product. In this stage, i.e. stage 2, the product water and substrate were collected daily at the outlet and bottom of each wetland. After the treatment process, the pH of the product water was observed to have increased from 2.6 to 10.4. Significant removal of inorganic contaminants was also observed and the following removal sequence was registered, Fe (99.8%) ≥ Al (99.5%) ≥ Mn (99.24%) ≥ Zn (98.36%) ≥ Cu (97.38%) ≥ Ni (97.7%) ≥ SO42─ (80.59%). Reduction in electrical conductivity (EC) was also observed (86%). Specifically, the nano-part removed the metals and sulphate partially whereas the bio-part effectively removed SO42─ and EC levels, thus denoting stellar combination and complementary performance for the hybrid system in integrated fashion. The state-of-the-art analytical instruments were used to underpin and succinct the fate of chemical species in raw and product MgO-NPs, substrates, and the grass. Finally, the product water conformed to the prescribed standards for effluent discharge hence proving that the synergy of neutralization and bio-remediation, i.e. nano-and-biotic system, could potentially yield the desired results in mine water management and afield. This will go a long way in curtailing ecological footprints associated with mining activities thus fostering the concept of sustainable development.

Developing a DEM and Elucidating through SWAT to Conserve Soil in Kulfo Watershed of Rift Valley Basin, Ethiopia

Due to uninterrupted erosion and transportation, huge volume of sediments carried away by streams and rivers are finally deposited on the meanders, lakes, and reservoirs when the velocity of the surface water flow decreases. Kulfo River in the southern part of Ethiopia faces a challenge due to massive deposit of sediments. Hydrometeorological and spatial data of Kulfo watershed from the observed stream flow data series near Kulfo bridge and four meteorological station data were used to assess the depositional environment of Kulfo watershed. The data length covers the period from 2000 to 2019. Geomorphic parameters of the watershed were developed by using a 30m × 30m digital elevation model (DEM). The spatial distribution of sediment yield of the study area was estimated using SWAT, the soil and water assessment tool. Scenarios were developed to assess the effectiveness of watershed management interventions provided at the watershed and critical subwatershed level. The model genuinely replicated the observed discharge and sediment with an overall performance of 0.75 as measured by NSE. Twenty-one subbasins were created, and the observed average sediment yield was calculated as 11.9 ton/ha/y. The observed average sediment yield reduction at the hotspot subwatershed level postapplication of contouring, filter strip, terracing, and strip cropping were 40.79%, 57.94%, 66.02%, and 62.93%, respectively. By intricately analyzing, it can be referred that terracing is the best conservation measure to be incorporated into the affected subbasins.

Integrated Hydrological Modeling to Analyze the Effects of Precipitation on Surface Water and Groundwater Hydrologic Processes in a Small Watershed

The main objective of this study is to evaluate the performance of the integrated hydrological model, MIKE SHE in a small watershed to analyze the effect of two different precipitation sources on model outputs (groundwater elevation and surface water flows). The model was calibrated and validated with observed groundwater elevations and surface water flows measured at the United States Geological Survey (USGS) gage stations in the basin. The model calibration performance for surface water flows (R = 0.80, MAE= 0.20 m3/s, BIAS = −0.14 m3/s, NSE = 0.59) and groundwater elevations (R = 0.74, MAE = 0.45 m, BIAS = 0.08 m, NSE = 0.35) showed that the model was able to predict hydrological processes based on forcing variables in a small watershed. The analysis did not show the model with precipitation at the nearer (NOAA-Edwardsville) gauge station has better performance than the farther gauge station (NOAA-St. Louis). The quantitative analyses for the most sensitive model output variable suggested that precipitation uncertainties had noticeable impacts on surface water flows (0.81% to 11.19%), than groundwater elevations (0.06% to 0.07%), with an average of 6.71% and 0.66%, respectively. Our results showed noticeable differences in simulated surface water flows in spring (12.9%) and winter (36%) seasons compared to summer (11.4%) and fall (4.6%) as a result of difference (6% to 18%) in precipitation, which indicated that uncertainties in precipitation impact simulated surface water flows in a small watershed vary with different seasons. Our analyses have shown that precipitation affects the simulated hydrological processes and care should be taken while selecting input datasets (i.e., precipitation) for better hydrological model performance, specifically for surface water flows.

Using biodiversity response for prioritizing participants and service provisions in a payment-for-water-storage program in the Everglades basin

Hydrological changes can lead to biodiversity responses that are complex and challenging to quantify. We present a framework that uses biodiversity as a criterion to address “where to buy” and “how much to buy” in a payment-for-environmental-services (PES) program focused on water storage service in the Everglades basin, USA. The PES program was designed to pay for added water storage on private cattle ranchlands by raising the spillage level in drainage control structures to reduce surface flows. We predicted that increased hydration of previously drained wetlands would benefit biodiversity, a previously unquantified but desirable co-benefit of the original program, and that a PES program offering bundled services (e.g., storage and biodiversity) can better achieve restoration goals. We quantified desirable biodiversity services (abundance of native flora and fauna such as cover of wetland and forage plants, and abundance of fishes, amphibians, and macroinvertebrates), dis-services (e.g., abundance of invasive plants and mosquitos), and hydrologic signatures (e.g., wetland water depth, inundation area and duration) at four ranches to develop eco-hydrological relationships (models) between hydrological changes and biodiversity responses. Next, a hydrologic model (MIKE-SHE/MIKE-11) was used to predict surface and subsurface water levels and flows and resulting wetland hydrologic signatures for 13 water storage alternatives on the ranches, which were used as example PES proposals. A decision-support-system (DSS) was developed to integrate (i) storage predicted by the hydrologic model, (ii) biodiversity responses predicted by eco-hydrologic models, and (iii) a user-defined preference scheme to assign importance weights to storage, biodiversity, and implementation cost. The DSS calculated a cumulative score for ranking PES proposals. By considering desirable services and dis-services, stakeholders can decide on their preferred level of services, e.g., buyer(s) may settle for less storage if there is a gain in desirable biodiversity. The DSS can identify trade-offs among services, helping stakeholders negotiate.

Numerical Simulations of the Cabbeling Phenomenon in Surface Gravity Currents in Cold Fresh Water

The behaviour of warm water discharge at a temperature higher then Tm horizontally into a homogeneous body of cold fresh water at a temperature lower then Tm was investigated by means of a numerical model. Water density here was taken to be a quadratic function of temperature. Thus cabbeling process was inevitable as positively buoyant water form surface current while penetrating the ambient water. The current halted as mixture became dense and sink. These results are very similar to the experimental study of warm discharge into cold water by Marmoush et al. [14] and Bukreev [22]. The results showed an initially sinking water at the point where the two water bodies meets within the first few time interval. Development of Rayleigh-Taylor instabilities was observed at the lower part of the surface current as lighter fluid penetrate further. The frontal head was found to being replenished by a surface flow of warm unadulterated water, but after much entrainment of ambient fluid and cabbeling then, this head halted and sink. On the floor, denser fluid advance in the same direction as the original surface current, with some degree of Kelvin-Helmholtz instability as it penetrates further. Relations were also drawn that describes the speed, the spread length of both surface current were obtained.
 Relation were also drawn that describes the final spread length of the surface current Lsm and the time taken to reach that final spread length Tsm as a function ϕin. This work as presented here is practical and relevant to many fields of study and also enhances policy making towards the protection of the aquatic ecosystems.

Modelling of waves and wave-induced currents in the vicinity of submerged structures under regular waves using nonlinear wave-current models

The evolution of waves and wave-induced currents around submerged structures under regular waves is simulated using two nonlinear wave-current models (Boussinesq-type); coupled with a one equation turbulence closure model to simulate the energy dissipation due to wave breaking. The first model is utilized to simulate the evolution of waves and wave-induced currents around porous structures, while the second model is used to simulate those around impermeable structures. The equation of motion for the porous medium in the first model incorporates an empirical Forchheimer-type term for laminar and turbulent frictional losses and inertial term to account for acceleration effects. In both models, an artificial energy dissipation term is introduced to overcome unrealistic flow patterns and surface water fluctuations, which lead to numerical instabilities near steep faces of submerged structures. In the present study, an improved wave breaking sub-model is introduced in 2DH, and the predictive skills of two improved models are investigated with a published and a new set of experimental data. The comparison between simulations and laboratory data show promising results for the wave height, mean-water level and current distribution around submerged structures for 2DH wave propagation.

Least-Cost Provision of Ecosystem Services from Water: When, Where, and How Much?

Changes in surface or groundwater management influence water use patterns as well as the economic value and sustainability of all water uses. In water-scarce regions, programs that establish environmental flows usually involve reallocating water from another productive use. Few peer-reviewed papers to date have investigated impacts on system-wide economic performance resulting from environmental flow regimes. This work presents an original approach to address that gap by developing and applying a basin-scale hydroeconomic optimization model of North America’s Middle Rio Grande Basin to explore impacts of environmental pulse flows on the region’s economy and water stocks. The model accounts for surface and groundwater storage, irrigation, urban, recreational, and environmental demands; surface water inflows under various climate scenarios; groundwater pumping and recharge; substitute water prices; crop water use; evaporation; as well as institutional constraints governing water use. Results show that climate change, in the form of highly variable inflows, has an impact on the total and marginal cost of implementing environmental pulse flows, amplified by the conjunctive nature of the system.

Along‐Orbit Analysis of GRACE Follow‐On Inter‐Satellite Laser Ranging Measurements for Sub‐Monthly Surface Mass Variations

AbstractWe examined the sensitivity of GRACE Follow‐On (GRACE‐FO) laser ranging interferometer (LRI) measurements to sub‐monthly time‐variable gravity (TVG) signals caused by transient, high‐frequency mass changes in the Earth system. GRACE‐FO LRI provides complementary inter‐satellite ranging measurements with higher precision over a wider range of frequencies than the baseline K‐band microwave ranging system. The common approach for studying mass variation relies on the inverted TVG or mascon solutions over a period of, for example, one month or 10 days which are adversely affected by temporal aliasing and/or smoothing. In this article, we present the alternative along‐orbit analysis methodology in terms of line‐of‐sight gravity difference (LGD) to fully exploit the higher precision LRI measurements for examination of sub‐monthly mass changes. The discrepancy between “instantaneous” LGD LRI observations and monthly‐mean LGD (from Level‐2 data) at satellite altitude indicates the sub‐monthly gravitational variability not captured by monthly‐mean solutions. In conjunction with the satellite ocean altimetry observations, high‐frequency non‐tidal atmosphere and ocean models, and hydrology models, we show that the LGD LRI observations detect the high‐frequency oceanic mass variability in the Argentine Basin and the Gulf of Carpentaria, and sub‐monthly variations in surface (river) water in the Amazon Basin. We demonstrate the benefits gained from repeat ground track analysis of GRACE‐FO LRI data in the case of the Amazon surface water flow. The along‐orbit analysis methodology based on LGD LRI time series presented here is especially suitable for quantifying temporal and spatial evolution of extreme, rapidly changing mass variations.

PRELIMINARY STUDY ON THE GROUNDWATER RESOURCES OF THE KORAMA SUB-WATERSHED IN THE COMMUNE OF DOGO-DOGO/ZINDER REGION: HYDROGEOLOGICAL CHARACTERIZATION AND GROUNDWATER QUALITY

The commune of Dogo-dogo is located in the extreme south of the Zinder Region, in a sub-catchment area of the Korama River, between 12°50 and 13°00 North latitude and 9°10 and 9°32 East longitude. This area is hydrogeologically based on the aquifers of the Malawa sandstone formations, characterized by an important potential groundwater resource and an abundant ecosystem, and has been subjected for years to the phenomena of climate change, the dynamics of land use and a galloping demography. This has resulted in changes in the quantity and quality of the water resource in this area. However, it seems necessary to undertake quantitative and qualitative studies of this resource. The main objective of this study is the hydrogeological and qualitative characterization of groundwater in the town of Dogo-dogo. The methodology adopted was based on the processing and statistical analysis of hydrogeological, chemical and bacteriological data, the elaboration of a piezometric map and a hydrogeological cross-section, which led to the following results The depths of the works vary from 45 to 97 m with an average of 68.73 m giving rise to water column thicknesses of more than 20 m. While, the values of water exploitation flows are very disparate, they vary from 0,3 to 24 m3/h with an average of 5,05 m3/h. Furthermore, the piezometric map shows that the direction of groundwater flow is generally from NW to SE. This general trend tends to follow the direction of flow of surface water, whose hydrographic network is more or less fossilized (Korama). As for the bacteriological results of the water, out of the 111 samples, 84 and 72 show respectively Total Coliforms (TC) and Escherichia. Coli in the groundwater. This could be explained by the lack of hygiene around the water points in conjunction with the shallow depths of the water in some places. All these aspects can compromise the drinking water supply of the populations. Finally, from the chemical point of view on the 111 water samples, two (02) and three (03) of these samples are characterized respectively by Arsenic and Nitrate contents exceeding the WHO standard of water consumption.

Seasonally variable relationships between surface water temperature and inflow in the upper San Francisco Estuary

AbstractWater temperature and inflow are key environmental drivers in aquatic systems that are linked through a causal web of factors including climate, weather, water management, and their downstream linkages. However, we do not yet fully understand the relationship between inflow and water temperature, especially in complex managed systems such as estuaries. The San Francisco Estuary is the center of a critical water supply infrastructure and home to a deteriorating ecosystem with several declining fish species at the warm edge of their thermal range. We used generalized additive modeling of long‐term monitoring data to evaluate the relationship between inflow and water temperature along with its spatio‐seasonal variability. Most commonly, we found a negative temperature‐inflow relationship in which water temperatures increased as inflow decreased, up to 2°C from high‐ to low‐inflow years. However, the opposite (positive) relationship was observed in the winter months, and in the western (downstream) regions from July–September, up to − 1.2°C from high‐ to low‐inflow years. These results were upheld by models that included the long‐term temperature trend or used salinity as a proxy for location. Upstream factors likely played the biggest role in the summer when local precipitation is negligible, whereas local precipitation and the related weather conditions may drive much of the winter pattern. Although further mechanistic studies are needed to infer the direct effect of dam releases on water temperatures, these results provide a broader understanding of the impacts of flood and drought dynamics for those tasked with managing estuarine ecosystems.

A structure-preserving algorithm for surface water flows with transport processes

A structure-preserving algorithm for surface water flows with transport processes

Climate change impact on Lake Tana water storage, Upper Blue Nile Basin, Ethiopia

Temperature and precipitation trend fluctuations influence the components of the hydrological cycle and the availability of water supplies and result shift in the balance of lake water (lake level). Lake Tana is one of the water resources potential providing many services and threatened by human-induced and natural factors in Upper Blue Nile Basin, Ethiopia. So assessing the impacts of climate change on this water resource is a primary activity for water resource managers, researchers, and stakeholders to understand its potential for the water resource. This study was therefore conducted to examine the implications of the influence of climate change on the water balance of Lake Tana (water level) using potential simulated climate production downscaled by a regional CORDEX climate model powered by GCM-RCM ensembles under the Eastern Africa domain CIMP5 archive (AFR44) and RCP scenarios (RCP4.5, and RCP8.5) for future climate data prediction. Quantile mapping has been used to correct temperature biases, and power transformation was applied for rainfall correction. The performance of the HBV model was evaluated through calibration and validation using objective functions (relative volume error (RVE), Nash-Sutcliffe Efficiency (NSE) and provide RVE of 3.7%, −1.27%, 1.05%, −0.72%, 8.9% and −0.68 during calibration and RVE of −1.5%, 6.93%, −3.04%,8.796%, −5.89% and 8.5% during validation for Gumara, Kiltie, Koga, Gilgel Abay, Megech and Rib respectively. While the model provided NS of 0.79, 0.63, 0.72, 0.803, 0.68 and 0.797 during calibration and NSE of 0.8, 0.64, 0.7, 0.82, 0.801 and 0.82 during validation for Gumara, Kiltie, Koga, Gilgel Abay, Megech, and Rib respectively. The simulated Lake level showed adequate agreement to the observed with NS and RVE of 0.7 and 6.44% respectively. The result showed that lake evaporation and rainfall increase for all future scenarios. The ungauged surface inflow is also increased shortly scenarios while gauged surface inflow increased for RCP4.5 (the 2070s) and RCP8.5 (2040s) and decreased for RCP4.5 (2040s) and RCP8.5 (2070s). The decrease in gauged surface water inflow is due to a decrease in inflow for Gilgel Abay, Koga and Gumara gauged catchments. The results showed that the Lake storage will decrease in all future scenarios of all-time horizons. As the study's revealed climate model minimized the level of uncertainty, especially with the use of more RCMs than GCMs, future studies should therefore use more than one regional climate model and also use fine resolution data like (CMIP 6).

Nonlinear Turbulent Two-Dimensional Shallow-Water Equations And Their Numerical Solution

Free surface flow of water over a shallow rough bed is characteristically turbulent due to disturbances generated by the bed resistance and diverse causes. The paper presents a derivation of the basic equations in two dimensions and their numerical solution by an extension of the method developed earlier for flow in one dimension. Starting from the three dimensional Reynolds Averaged Navier Stokes (RANS) equations, the equations of continuity and horizontal momenta are depth averaged to derive three equations for the free surface elevation ζ and the horizontal, depth averaged velocity components (U, V ). Certain closure assumptions are required for derivation of the equations. Principally, the viscous stresses are neglected, while the Reynolds stresses are assumed to depend on the vertical coordinate z only for the shearing flow over the x, y - plane representing the plane bed. Secondly, it is assumed that the instantaneous horizontal components of velocity (u, v) follow the 1/pth (p = 7) power law of variation in the z - direction, in liu of the the logarithmic law of the wall. For numerical solution of the three nonlinear equations of continuity and momenta, the equations are reformulated in terms of the primitive “discharge” components (Q, R) of the velocity (U, V ), showing that Q and R can be functions of ζ alone. The transformed equation of continuity is treated by the Lax-Richtmyer method. The two momentum equations on the other hand, transform in to two coupled second degree equations in the derivatives of Q and R, which decouple in the important case of quasilinear straight crested waves on the water surface. The decoupled equations are numerically solved by the iterative modified Euler.

Behavioural responses of threespine stickleback with lateral line asymmetries to experimental mechanosensory stimuli.

Behavioural asymmetry, typically referred to as laterality, is widespread among bilaterians and is often associated with asymmetry in brain structure. However, the influence of sensory receptor asymmetry on laterality has undergone limited investigation. Here we used threespine stickleback (Gasterosteus aculeatus) to investigate the influence of lateral line asymmetry on laterality during lab simulations of three mechanosensation-dependent behaviours: predator evasion, prey localization and rheotaxis. We recorded the response of stickleback to impacts at the water surface and water flow in photic conditions and low-frequency oscillations in the dark, across four repeat trials. We then compared individuals' laterality with asymmetry in the number of neuromasts on either side of their body. Stickleback hovered with their right side against the arena wall 57% of the time (P<0.001) in illuminated surface impact trials and 56% of the time (P=0.085) in dark low-frequency stimulation trials. Light regime modulated the effect of neuromast count on laterality, as fish with more neuromasts were more likely to hover with the wall on their right during illumination (P=0.007) but were less likely to do so in darkness (P=0.025). Population-level laterality diminished in later trials across multiple behaviours and individuals did not show a consistent side bias in any behaviours. Our results demonstrate a complex relationship between sensory structure asymmetry and laterality, suggesting that laterality is modulated by multiple sensory modalities and is temporally dynamic.