Multi-Model Approach for Assessing the Influence of Calibration Criteria on the Water Balance in Ouémé Basin

Hydrological models are very useful tools for evaluating water resources, and the hydroclimatic hazards associated with the water cycle. However, their calibration and validation require the use of performance criteria which choice is not straightforward. This paper aims to evaluate the influence of the performance criteria on water balance components and water extremes using two global rainfall-runoff models (HBV and GR4J) over the Ouémé watershed at the Bonou and Savè outlets. Three (3) Efficacy criteria (Nash, coefficient of determination, and KGE) were considered for calibration and validation. The results show that the Nash criterion provides a good assessment of the simulation of the different parts of the hydrograph. KGE is better for simulating peak flows and water balance elements than other efficiency criteria. This study could serve as a basis for the choice of performance criteria in hydrological modelling.

Flood Risk Assessment in the Lower Valley of Ouémé, Benin

In response to the increased frequency of flood events in recent years, it has become crucial to enhance preparedness and anticipation through precise flood risk assessments. To this end, this study aims to produce updated and precise flood risk maps for the Lower Valley of Ouémé River Basin, located in the South of Benin. The methodology used consisted of a combination of geographical information systems (GIS) and multi-criteria analysis, including Analytical Hierarchy Process (AHP) methods to define and quantify criteria for flood risk assessment. Seven hydro-geomorphological indicators (elevation, rainfall, slope, distance from rivers, flow accumulation, soil type, and drainage density), four socio-economic vulnerability indicators (female population density, literacy rate, poverty index, and road network density), and two exposure indicators (population density and land use) were integrated to generate risk maps. The results indicate that approximately 21.5% of the Lower Valley is under high and very high flood risk, mainly in the south between Dangbo, So-Ava, and Aguégués. The study findings align with the historical flood pattern in the region, which confirms the suitability of the used method. The novelty of this work lies in its comprehensive approach, the incorporation of AHP for weighting factors, and the use of remote sensing data, GIS technology, and spatial analysis techniques which adds precision to the mapping process. This work advances the scientific understanding of flood risk assessment and offers practical insights and solutions for flood-prone regions. The detailed flood risk indicator maps obtained stand out from previous studies and provide valuable information for effective flood risk management and mitigation efforts in the Lower Valley of Ouémé.

Assessment of the Recent Hydromorphological Features of Nokoue Lake and Its Channels (South-East Benin)

Based on 2022 and 2023 hydrometric data and satellite images (Sentinel 2022, SPOT 2010), this study aims to present the Nokoué Lake and its channels’ re-cent hydromorphological characteristics. Integrating flow, tributary morphology, and topography data determined specific power values along the axes studied. The values obtained range from 2.69 to 12.92 W/m2 for Ouémé River and 2.46 to 10.99 W/m2 for Sô River. The resulting water erosion on banks and bottoms is of linear, areolar, or gully and claw types. Lake bathymetry varies from -0.5 to -2.6 m (low flow period) and -1 to -4 m;in the Ouémé, Sô, and Totchè rivers, it varies from -5 m to -7 m, reaching -10 m at the Cotonou channel entrance (flood period). Bathymetric profiles reveal varied “U”, “V” and “Intermediate” bottom morphologies, influenced by erosion/sedimentation processes and human activities. The flow facies identified are lentic in the northern tributaries and lotic in the Cotonou and Totchè canals. Spatial analysis identified nine (09) thematic classes. In 2022, the surface area of the water body has increased from 274 km2 at low water to 280 km2 at high water, whereas in 2010 (a recent year of exceptional flooding), the surface area was 270 km2 at low water and 277 km2 at high water. Significant changes in land use are observed between 2010 and 2022. The floodplain area decreased slightly, from 421 km2 in 2010 (year of exceptional flooding) to 419 km2 in 2022. The evolution of land use shows a progressive expansion of the urban environment to the detriment of the natural environment. In the medium to long term, this trend could threaten the hydromorphological balance and even the existence of this important lagoon ecosystem.

Study of the Physico-Chemical and Bacteriological Characteristics of Drinking Water in So-Ava,South Benin

The present study assesses the physicochemical and bacteriological quality of the drinking water used by the population of S?-Ava based on the Beninese standards and those established by the World Health Organization (WHO). In rural and peri-urban areas of Benin where public water supply systems are inadequate or almost non-existent, the population consumes water of various sources of unknown qualities. A total of 67 water samples were analyzed during the rainy season (July 2017) and in the dry season (January 2018) for certain physical, chemical and bacteriological parameters using the standard methods. The results of the analyses reveal that the physicochemical characteristics of the water used for consumption in S?-Ava comply with the drinking water standards of the World Health Organization and those in force in Benin except for the percentages of the following parameters: pH (41.80%);turbidity (25.37%);the color (16.42);ammonium (17.91%);iron (40.30%);Nitrites (4.48%);Residual chlorine (91.05). Bacteriologically, the analyses showed a high total aerobic mesophilic flora contamination, faecal coliforms, E. coli, faecal enterococci respectively in 89.55%, 82.09%, 50.75% and 70.15% of the analyzed water samples. The ratio of faecal coliforms to faecal enterococci indicated that the origin of faecal contamination was human in 59.7% of the samples and animal in 40.3% of the samples. The adoption of hygiene measures at the water point, during the transport and storage of water, including the treatment by chlorination of drinking water at the family level was recommended for the population concerned and household awareness on the adoption of basic hygiene and sanitation measures have been recommended for hygiene and sanitation services.

Sediment Speciation from Dekin Groundwater at District of Dangbo (South Benin)

The objective of this research is to determine the physicochemical elements contained in the groundwater and in the deposits originating from these waters of the Arrondissement of Dêkin, Commune of Dangbo in the South of Benin. Physical parameters were measured from the multi-parameter and the chemical parameters by reagent assays. The precipitate from the groundwater was studied by speciation. The different assays were carried out using the Hach Lange DR2800 Spectrophotometer. The data processing was done with different software including ArcGis 10.1, Diagram.Ink of Roland SIMLER and PHREEQC 2.17.4137. Strong mineralization of the deposit from the drilling water was indicated in these three elements: Copper (220.1 mg/kg), iron (2528 mg/kg) and zinc (239.5 mg/kg) whose contents are higher than the French guideline values for heavy metal content in sediments in mg/kg. The calculation of the Saturation Indices of the drilling water shows saturation with respect to Goethite and Hematite. All these results have led us to conclude that the high content of Metallic Trace Element (MTE) in the deposit and especially of the iron in the drilling water originates from the dissolution-precipitation of the aquifer rock.

An Adaptive Estimation of Forecast Error Covariance Parameters for Kalman Filtering Data Assimilation

An adaptive estimation of forecast error covariance matrices is proposed for Kalman filtering data assim- ilation. A forecast error covariance matrix is initially estimated using an ensemble of perturbation forecasts. This initially estimated matrix is then adjusted with scale parameters that are adaptively estimated by minimizing -2log-likelihood of observed-minus-forecast residuals. The proposed approach could be applied to Kalman filtering data assimilation with imperfect models when the model error statistics are not known. A simple nonlinear model （Burgers＇ equation model） is used to demonstrate the efficacy of the proposed approach.

Potential groundwater recharge zones within New Zealand

Water resources in New Zealand are not evenly distributed across the country which makes it difficult to adequately allocate the use of water resources in every basin. Groundwater is a fundamental water resource in New Zealand for agricultural, industrial and domestic use. Detailed knowledge regarding groundwater recharge potential is a pre-requisite for sustainable groundwater management, including the assessment of its vulnerability to contamination by pollutants. In this study, a comprehensive GIS approach was used to map the potential groundwater recharge zones across New Zealand. National data sets of lithology, slope, aspect, land use, soil drainage and drainage density were converted to raster data sets with a spatial resolution of 500 m x 500 m and superimposed to derive groundwater potential zones. The resultant maps demonstrate that the potential is low in urban and mountainous areas, such as the Southern Alps, whereas the highest potential can be found in regions with large lakes and in the lower elevation plains areas, where Quaternary sediments prevail. The resulting maps can be used to identify areas of high nutrient leaching in zones where high groundwater recharge potential exists.

Spatio-Temporal Analysis of Climate Change Impact on Future Wind Power Potential in Burundi (East Africa)

This paper assessed climate change impact on future wind power potential across highlands and western lowlands of Burundi. Hourly observed and MERRA-2 data were considered for the historical period 1980-2016, and a Multi-model ensemble for future projections data of eight selected Regional Climate Models under RCP 4.5 and RCP 8.5 over the periods 2019-2040 and 2071-2100 was used. Variability and trend analysis were adopted using standardized index and Mann-Kendall’s test, respectively while wind power density (WPD) in quartiles was adopted for changes distribution. As results, diurnal wind speeds (WS) were higher from 9:00 AM to 2:00 PM, while monthly wind speeds reached the maximum during summer time. An increasing trend in WPD was detected all over the studied area. Over the period 2019-2040, the lowest WPD change is projected at Northern Highlands (NHL) under RCP 4.5 with 28.04 W·m−2 while the highest WPD change of 47.35 W·m−2 is projected under RCP 8.5 at Southern Imbo plain (SIP). As for the period 2071-2100, the highest change is expected at SIP under RCP 8.5 with 152.39 W·m−2 while the minimum change of 83.96 W·m−2 is projected under RCP 4.5 at NHL. The findings showed that areas nearby the Lake Tanganyika are expected to have high positive WDP changes.

A Structural Overview through GR(s) Models Characteristics for Better Yearly Runoff Simulation

In rainfall-runoff modelling, a monthly timescale and an annual one are sufficient for the management of deductions. However, to simulate the flow at a large time-step (annual), we generally precede the use of a model working for a finer time-step (daily) while aggregating the desired outputs. The finest time-steps are considered, apriori, as the most performant. By passing from one time-step to another, and in order to work in the desired time-step (annual) and calculate the potential gains or loss, this article proposed a comparative study between the aggregation method of outputs of a modal working at a finer time step, and a method in which we use a conceived model from the beginning. To ensure this comparative and empirical approach, the choice has been focused on (GRs) models to a daily time-step (GR4J), monthly time step (GR2M) and annual time step (GR1A). The modelling platform used is the same for all three models taking into account the specificities of each one: the same data sample, the same optimization method, and the same function criterion are used during the construction of these models. Due to the moving between these time steps, results show that the best way to simulate the annual flow is to use an appropriate and designed modal initially conceived to this time step. Indeed, this simulation seems to be less effective when using a model at a finer time-step (daily).

Physico-Chemical Features of the Kpassa Reservoir, Northern Benin, with Emphasis on Its Trophic State: A Preliminary Study

This work presents recent data on the physico-chemical properties and the trophic status of Kpassa reservoir at eighteen locations from August 2014 to February 2015. Seventeen physico-chemical parameters were measured and data obtained were statistically analyzed. The descriptive statistics showed their variations (minima-maxima) as follows: pH (4.65 - 7.30), temperature (25.1°C - 29.9°C), dissolved oxygen (1 - 5.79 mg/L), oxydability (0.32 - 10.88 mg O2/L), electrical conductivity (55 - 77 μS/cm𕒵), TDS (76 - 94 mg/L), turbidity (15.70 - 274.40 NTU), transparency (0.24 - 1.55 m), suspended matter (3 - 92 mg/L), total phosphorus (0.25 - 1.90 mg/L), orthophosphate (0.08 - 0.61 mg/L), nitrate (undetected 5.50 mg/L), nitrite (undetected 0.79 mg/L), ammonia (undetected 0.36 mg/L), chlorophyll a (7.20 - 2334.6 μg/L), silica (4.34 - 15.67 mg/L) and N/P ratio (0.08 - 42.62). These parameters were mainly influenced by agricultural activities and climatic conditions. The restriction or the removal of the use of chemical fertilizers in agricultural activities in Kpassa reservoir basin was recommended. The highest values of Pearson and Spearman correlations were observed across TDS and conductivity (0.967;0.951), turbidity and oxydability (0.924;0.665), turbidity and chlorophyll a (0.884;0.663), turbidity and suspended matter (0.982;0.793), suspended matter and transparency (𕒴.781;𕒴.819), suspended matter and nitrate (𕒴.813;𕒴.839), suspended matter and oxydability (0.919;0.602) and suspended matter and chlorophyll a (0.879;0.656). Carlson’s trophic state index (TSI) values varied between 36 and 66 showing that Kpassa reservoir was eutrophic in August and mesotrophic to oligotrophic during the other months of the sampling period. ANOVA and Kruskal-Wallis test indicated that there were no significant differences between sampling stations.

Assessment of the Risk of Toxicity of Fish in the River So by Contamination in Heavy Metals(Southern Benin,West Africa)

The purpose of this study is to assess the state of contamination of fish in the S? River by trace metal elements including Zinc, Lead, Cadmium, Copper and Arsenic. Water samples and four species of both sexes (Clarias anguillaris, Kribia kribensis, Tilapia guineensis and Eleotris vittata) were collected and analyzed. The pH, temperature and values of the chemical species present in the water of the S? River characterize an ecosystem favorable to the growth of aquatic species. The Metallic Traces Elements (MTE) concentrations vary from one fish species to another and depend on the sex and age of the animal. Zinc and copper are more concentrated in males than females with the exception of copper in Tilapia. The Pb concentration is higher in young Kribia and Clarias as well as Zn and Cd in young Tilapia. The concentrations in Cd and Pb are well above the European standards and those in the Republic of Benin, worrying results that express a health toxicity risk related to the consumption of fish of the river S?.

Nitrogen pollution and source identification of urban ecosystem surface water in Beijing

Nitrogen contamination of surface water is a worldwide environmental problem with intensive agricul- ture and high population densities. We assessed the spatial and seasonal variation in concentrations of total nitrogen and different nitrogen species present in surface-water in Beijing, China. Also, chemical （NO3-N/C1-） and isotopic （615Nnitrate） indicators were used to identify nitrate sources. The results showed that, during 2009 and 2010, nitrate nitrogen concentrations ranged from 0.7 to 7.6 mg· L^-1, ammonium nitrogen from 0. I to 3.4 mg· L^-1, and total nitrogen from 2.4 to 17.0mg· L^-1. Inorganic nitrogen accounted for between 60 and 100% of total nitrogen at the ten monitoring sites. Nitrate nitrogen, ammonium nitrogen, and total nitrogen concentrations at the 2 downstream monitoring sites in south-eastern Beijing were significantly higher than those at the other eight upstream monitoring sites （P 〈 0.01）. Examination of seasonal variation showed that there was a significant inverse relationship between nitrate nitrogen concentrations and precipitation, and that nitrate nitrogen concentrations peaked in the dry seasons. The information given by the 15Nnitrate values and nitrate nitrogen concentrations, combined with the NO3-N/C1- ratio distribution, showed that domestic sewage was the major source of nitrate in Beijing. Methods to control and reduce sewage pollution are urgently needed to help manage surface water quality in Beijing.

Climate change in the Tianshan and northern Kunlun Mountains based on GCM simulation ensemble with Bayesian model averaging

Climate change in mountainous regions has significant impacts on hydrological and ecological systems. This research studied the future temperature, precipitation and snowfall in the 21^（st） century for the Tianshan and northern Kunlun Mountains（TKM） based on the general circulation model（GCM） simulation ensemble from the coupled model intercomparison project phase 5（CMIP5） under the representative concentration pathway（RCP） lower emission scenario RCP4.5 and higher emission scenario RCP8.5 using the Bayesian model averaging（BMA） technique. Results show that（1） BMA significantly outperformed the simple ensemble analysis and BMA mean matches all the three observed climate variables;（2） at the end of the 21^（st） century（2070–2099） under RCP8.5, compared to the control period（1976–2005）, annual mean temperature and mean annual precipitation will rise considerably by 4.8°C and 5.2%, respectively, while mean annual snowfall will dramatically decrease by 26.5%;（3） precipitation will increase in the northern Tianshan region while decrease in the Amu Darya Basin. Snowfall will significantly decrease in the western TKM. Mean annual snowfall fraction will also decrease from 0.56 of 1976–2005 to 0.42 of 2070–2099 under RCP8.5; and（4） snowfall shows a high sensitivity to temperature in autumn and spring while a low sensitivity in winter, with the highest sensitivity values occurring at the edge areas of TKM. The projections mean that flood risk will increase and solid water storage will decrease.

Integrated bioremediation techniques in a shrimp farming environment under controlled conditions

This study investigated the integrated bioremediation techniques for a shrimp culture system to reduce unconsumed feed and the contents of suspended solids（SS）, nutrients and organic pollutants using barracuda,clamworm, scallop, large algae and a biofilter. A multi-pool internal circulation system was designed to test the effectiveness of the techniques in the laboratory. The experimental result has shown that Argopecten irradians,Gracilaria lemaneiformis and the biofilter efficiently reduced the contents of SS, dissolved inorganic carbon（DIC）and dissolved organic carbon（DOC） in the breeding wastewater. The amount of unconsumed feed was significantly reduced by barracuda and clamworm, but there was an increase in the contents of SS, DIC and DOC in the water due to disturbance by the barracuda and clamworm. The capacity of macroalgae to extract inorganic nitrogen was insufficient. However, the balance of the nitrogen fixation rate of macroalgae and the biological exhaust nitrogen rate within the system should be fully considered. The use of the biofilter alone was not optimal for the remediation of organic matter in shrimp effluent so that auxiliary foam separation technology is needed to improve the ability of the system to remove macromolecules. This study provides a basis for the further development of remediation techniques to reduce the environmental impact of shrimp aquaculture.

Evaluation of the Microbiological Quality of Drinking Water and Health Risks in the Commune of Sô-Ava, in Southern Benin (Evaluation De La QualitéMicrobiologique Des Eaux De Boisson Et Risques Sanitaires Dans La Commune De Sô-Ava, Au Sud-Bénin)

Access to drinking water in rural and semi-rural areas is a major concern for the populations because of the quality of the resources. This research work aims to analyze the bacteriological quality of the water consumed by households in the Commune of Sô-Ava in order to establish a relationship between this quality and the health problems observed within the communities. To succeed in this study, documentary research, surveys and observations in the field and analyzes of eighty-two (82) water samples were analyzed in the laboratory during two (2) seasons (rainy and dry). From the results obtained, it appears that the samples present concentrations of total germs, faecal coliforms, Escherichia coli, faecal enterococci, sulphite-reducing anaerobic bacteria (ASR), salmonella and Shiguela which do not comply with the water potability standards in respectively 78.05%, 60.98%, 50%, 64.63%, 80.49% and 70.73% of the samples taken. The statistics on the diseases recorded during this decade in the Commune showed that the populations of Sô-Ava are confronted with several ailments such as: malaria (75%), Acute Respiratory Infections IRA, (16%) and Gastrointestinal disorders (5%) especially during floods and during the rainy season. Education and sensitization of the population on good public hygiene practices around water must be highlighted in order to avoid waterborne diseases.

Nitrate in shallow groundwater in typical agricultural and forest ecosystems in China,2004-2010

The nitrate-nitrogen（NO 3-N） concentrations from shallow groundwater wells situated in 29 of the Chinese Ecosystem Research Network field stations,representing typical agroand forest ecosystems,were assessed using monitoring data collected between 2004 and 2010.Results from this assessment permit a national scale assessment of nitrate concentrations in shallow groundwater,and allow linkages between nitrate concentrations in groundwater and broad land use categories to be made.Results indicated that most of the NO 3--N concentrations in groundwater from the agroand forest ecosystems were below the Class 3 drinking water standard stated in the Chinese National Standard：Quality Standard for Ground Water（≤ 20 mg/L）.Over the study period,the average NO 3--N concentrations were significantly higher in agro-ecosystems（4.1 ± 0.33 mg/L） than in forest ecosystems（0.5 ± 0.04 mg/L）.NO 3-N concentrations were relatively higher（〉 10 mg N /L） in 10 of the 43 wells sampled in the agricultural ecosystems.These elevated concentrations occurred mainly in the Ansai,Yucheng,Linze,Fukang,Akesu,and Cele field sites,which were located in arid and semiarid areas where irrigation rates are high.We suggest that improvements in N fertilizer application and irrigation management practices in the arid and semi-arid agricultural ecosystems of China are the key to managing groundwater nitrate concentrations.

Surface and tropospheric ozone trends in the Southern Hemisphere since 1990: possible linkages to poleward expansion of the Hadley circulation

Increases in free tropospheric ozone over the past two decades are mainly in the Northern Hemisphere that have been widely documented,while ozone trends in the Southern Hemisphere(SH)remain largely unexplained.Here we first show that in-situ and satellite observations document increases of tropospheric ozone in the SH over 1990–2015.We then use a global chemical transport model to diagnose drivers of these trends.We find that increases of anthropogenic emissions(including methane)are not the most significant contributors.Instead,we explain the trend as due to changes in meteorology,and particularly in transport patterns.We propose a possible linkage of the ozone increases to meridional transport pattern shifts driven by poleward expansion of the SH Hadley circulation(SHHC).The SHHC poleward expansion allows more downward transport of ozone from the stratosphere to the troposphere at higher latitudes,and also enhances tropospheric ozone production through stronger lifting of tropical ozone precursors to the upper troposphere.These together may lead to increasing tropospheric ozone in the extratropical SH,particularly in the middle/upper troposphere and in austral autumn.Poleward expansion of the Hadley circulation is partly driven by greenhouse warming,and the associated increase in tropospheric ozone potentially provides a positive climate feedback amplifying the warming that merits further quantification.

PyLUR:Efficient software for land use regression modeling the spatial distribution of air pollutants using GDAL/OGR library in Python

Land use regression(LUR)models have been widely used in air pollution modeling.This regressionbased approach estimates the ambient pollutant concentrations at un-sampled points of interest by considering the relationship between ambient concentrations and several predictor variables selected from the surrounding environment.Although conceptually quite simple,its successful implementation requires detailed knowledge of the area,expertise in GIS,statistics,and programming skills,which makes this modeling approach relatively inaccessible to novice users.In this contribution,we present a LUR modeling and pollution-mapping software named PyLUR.It uses GDAL/OGR libraries based on the Python platform and can build a LUR model and generate pollutant concentration maps efficiently.This self-developed software comprises four modules:a potential predictor variable generation module,a regression modeling module,a model validation module,and a prediction and mapping module.The performance of the newly developed PyLUR is compared to an existing LUR modeling software called RLUR(with similar functions implemented on R language platform)in terms of model accuracy,processing efficiency and software stability.The results show that PyLUR out-performs RLUR for modeling in the Bradford and Auckland case studies examined.Furthermore,PyLUR is much more efficient in data processing and it has a capability to handle detailed GIS input data.

Numerical Simulation Study on the Scientific and Methodological Aspects of the Brazilian Proposal

In this paper, by using a simple climate model (SCM), a numerical simulationstudy has been conducted on the scientific and methodological aspects of Brazilian Proposal. Firstthe initial check of simple climate model has been done, then we do some sensitivity studies ontimeframes (attribution start and end dates, and evaluation date), and three attribution methods(marginal attribution method, proportional attribution method, and time-sliced attribution method),at last we get the main conclusions as follows: The simple climate model can represent the resultsof more complex climate model (e.g., HadCM3), and it is thus used to study the scientific andmethodological aspects of the Brazilian Proposal. Because of the limited knowledge of science anddata, although attributing a part of temperature increase to different GHG (greenhouse gas) emissionsource, there is considerable temperature increase unattributed to regional emissions. Therefore itis uncertain to make Brazilian Proposal as the method for the responsibility share of future GHGdecrease emission. The choices of different timeframes (attribution start and end dates, andevaluation date) and future emission SRES (Special Report on Emission Scenarios) make greatinfluence on the regional contributions to global climate changes, but different attribution methodshave only a little influence.