IRAN-WATER RESOURCES RESEARCH
Year:2018 | Volume:14 | Issue:1 |Papers Count:30

This paper deals with parameter estimation of SWAT model by means of streamflow data assimilation and application of calibrated model for hydrological simulation of Mahabad River leading to Urmia Lake. Data assimilation algorithem is compared with SUFI2 algorithem. SUFI2 is an uncertaintybased optimization method first developed for auto-calibration of environmental and water resource models. Due to availablity in SWAT-CUP package this is usually used for calibration of SWAT. To illustrate capabilities of data assimilation for calibration of the model and prediction of the river discharge, Ensemble Kalman Filter (EnKF) is utilized in a joint state-parameter estimation framework. Both coding EnKF and calling SWAT is done in MATLAB environment. Results showed that the joint state-parameter estimation using EnKF for SWAT, lead to improvement of accuracy of simulation and prediction of Mahabad River’s monthly discharge at Bitass hydrometery gauge compared to parameter estimation of the model using SUFI2.

Agricultural sector is the largest water consumer and uncertainty is an inevitable aspect of water management in this sector. In this study, fully fuzzy linear programming using two different solutions were applied for multi-objective optimizing of cropping pattern and net benefit in the uncertain conditions for the Zarrinehroud Basin. The uncertainties within the optimized cropping pattern were considered using a fuzzy method. Moreover, in order to consider the uncertainties in the available water limitation, three different hydrological conditions were applied to determine maximum, average, and minimum of fuzzy bond. The results showed an increase of %2.53 in net benefit comparing to the crisp optimization and an increase of %36.34 comparing to the present cropping pattern through decreasing low income crops substituted by high income crops. It is also shown that applying fully fuzzy linear programming instead of crisp linear programming leads to a greater saving in water consumption with the amount of %88.22. Considering %10 and %20 uncertainty bands for optimization parameters caused more water saving and net benefits from optimal cropping pattern. Therefore, optimization of cropping pattern through considering uncertainties based on fuzzy method leads to a more optimal planning for agricultural water.

The importance of water as a vital element for the humanity included the access to water as a right in human rights. This right that formed in the light of the rights to life and health and became an independent right provided a new approach to the governance and water management in accordance with its widespread effects. In fact, human rights lead to the imposition binding obligations on the states which effect the water management by creating requirements to warrant the water rights and underlie the evolution of general principles which govern water management. This includes negative and positive aspects. The positive aspects emerges in the exercise of the right to water and the negative aspect acts in the protection of this right and in prevention of violation through appropriate management of water. This article studied the water management in the light of human rights in the purpose of creating relationship between these two aspects and gets help from human rights approach to improve the water management and explain its necessity. The study was based on descriptive and analytical methods according to the library and internet data.

Hydrological modeling needs climate data with high spatial accuracy especially in low-rainfall areas where usually there is a no-good observational network. Currently, the lack of climate observational data can somehow be overcome using gridded global databases. CRU and NCEP CFSR databases are amongst the most prestigious gridded databases which were evaluated in this study by using SWAT model for Maharlu Lake basin. Statistical index comparisons in 33 years (1980-2013) showed the accuracy of the two datasets with Nash Sutcliffe efficiency index as approximately 0.91 in monthly scale. The modeling was then conducted by SWAT for all three datasets. The modeling results showed that databases could have high accuracy in rainfall runoff modeling from which the CRU database indicated better runoff simulation compared to NCEP CFSR databases. Coefficients of determination and Nash Sutcliffe efficiency in each calibration and validation periods represented average values above 0.7 for observed datasets, 0.65 for CRU, and 0.6 for NCEP CFSR.

Groundwater resources have ever been one of the main freshwater suppliers in arid and semi-arid areas such as Iran. Urmia Lake’s basin located in East-Azerbaijan province, Iran, is one of the areas where a significant portion of the water demands is provided by groundwater. The present study considers the interaction of Urmia Lake and Ajabshir coastal aquifer in this province. Hence, a three-dimensional, heterogeneous and anisotropic model has been developed using a numerical code of SUTRA. The model has been applied after the calibration and verification procedures. The effects of decreased level in Urmia Lake, increasing this level to the ecological level, and increase or decrease in the net recharge rate of the aquifer on discharge to the aquifer from the lake and vice versa have been assessed. The results showed that decrease in the level of the lake with the rate of 0.4 m/year would decrease the average aquifer level by 1.7 m over 10-years period. Increasing the level of the lake to its ecological level would however increase the level of the aquifer by 0.75 m in average in 30-years. Also, 10 percent increase in net recharge rate would resulted in 1.8 m increase in the average water table during 30-years while 10 percent reduction in net recharge rate would cause the reduction of 1.7 m in the average groundwater level.

Doubtlessly hydroclimatic models play important role in the management of water resources. The hydroclimatic time series have three principle components (autoregressive, seasonality and stochastic) and the performance of the models are related to these components, In the current research, the wavelet transform was linked to the Holt-Winters (HW) model for prediction of monthly runoff in Lighvanchai (Iran), Trinity, and West Nishnabotna (US) watersheds and minimum temperature of Tabriz. The obtained results were compared with autoregressive and seasonal models such as ARIMA, seasonal ARIMA (SARIMA) and HW. For this purpose, the main time series were decomposed to some multi-frequency time series by wavelet transform. Then due to the univariated nature of the HW model, these subseries were imposed as input data to the HW models for two scenarios. In the first scenario only approximation subseries and one detail subseries (resulting from the accumulation of all details subseries) and in the second scenario all subseries were used as input to HW models. Results showed that the second scenario of hybrid wavelet-holtwinters model (WHW2) could lead to considerably increased accuracy of both runoff and temperature monthly modeling because of the multiscale analysis and considering all multi-frequency subseries.

This study employs cellular automata (CA) to deal with the optimal operation of multipurpose reservoir systems functioning for water supply to consumptive agricultural demands, hydropower generation and minimum environmental flow purposes. Discrete time instances (beginning of monthly time periods) are taken as cells and storage volumes at these instances are considered as the states of the cells. The CA updating rule is derived from the analytical optimization of the local objective functions in presence of nonlinear hydropower equations. Additionally, the sub-problem of the optimal water allocation to different downstream users is solved using Lagrange multipliers technique. The proposed method is used to solve the nonlinear, non-convex operation optimization of Balarud reservoir and its hydropower plant as a real case study. The performance of the method is compared with those of the gradient-based optimization methods and Genetic algorithm for periods of 5, 20 and 44 years. The results show that the proposed cellular automata-based optimization model is able to find solutions with acceptable quality from the optimality perspective while rendering considerable reduction in the required computational load.

This research aimed to identify and rank factors affecting Participative Management in an organization based on the Analytic Hierarchy Process (AHP) in Golestan Regional Water Authority. First, to investigate these factors, scientific texts and previous researches were reviewed and several meeting with reporters were held. The result of this stage has been classified in 20 effective factors of the Participative Management in 5 main categories. Finally, a hierarchical tree of decisions for research was prepared. Then by using a questionnaire based on pair comparisons (AHP specific questionnaire) 22 votes were taken form reporters and employed experts in Golestan Regional Water Authority and with the use of analysis hierarchical process (AHP) and the expert choice software, the major and minor factors were classified and scaled.The result showed that management factors with a relative weight of 0.292 was the most important factor in establishment of the Participative Management. Organizational structure executives factor, attitude to participation, and Information Technology with the respective weights of 0.248, 0.198, 0.146, and 0.116 held the second to fifth rank. Accordingly, the minor factors of each main subclass were classified and scaled. Then, according to these priorities for the establishment of the Participative Management in a statistical society, applied recommendations were forwarded.

Rivers as fresh water resources are exposed to different amounts of pollutants and therefore it is necessary to have awareness of qualitative variations in rivers. Using water quality indices is one of the methods for analysis of water quality. In this study, type and weight of the variables included in the valid national and international water quality indices were statistically examined. Then, the performance index curves of the variables were produced based on the various standards and guidelines. In the next stage, using the Delphi method 9 variables were selected as the effective variables for water resources in Iran and their weights were determined based on the analytical hierarchy process. Curves with high correlation coefficients were fitted to the quality values proposed by the specialists and geometric. Average function was employed for combination of sub indices and calculating the final value of the quality index. The value of the proposed quality index was calculated for the Karoun River and was compared with the other quality indices. According to the obtained results, interpretation of water quality in the Karoun River based on the presented new quality index differs from the other quality indices.

The purpose of this study was the evaluation of the effect of meteorological droughts on groundwater changes in Komijan aquifer. Using the information of 32 piezometric wells and three meteorological stations of Komijan, Ghahavand and Khondab located around the aquifer, the effects of meteorological droughts on groundwater resource index (GRI) were studied by the standardized precipitation index (SPI), the percentage of normal (PNI) and decides (DI). Assessments were based on Pearson correlation analysis on a monthly scale and the time lag of 1, 3, 6, 9, 12, 18, 24 and 48 months. The results showed that all three drought indexes with 9 month time lag had more effect on GRI index. Also, the percent of stations with significant correlation between GRI and SPI, DI and PNI were 20.14, 27.43 and 31.25 percent, respectively. The average of groundwater depth in dry and wet years indicated that drought phenomenon led to 1.17 m reduction in groundwater height.

One of the most important parameters of the water balance equation is evapotranspiration which is an effective factor in the management of water resources. As in many different sciences where hardware methods are widely being replaced by software methods, actual evapotranspiration is also being determined using remote sensing and satellite images. According to the importance of actual evapotranspiration in the allocation of water resources, in current research this parameter was determined for sugarcane by in Amir Kabir Sugarcane Argo-Industry using satellite images from Landsat8 (suitable spatial resolution) and MODIS (acceptable temporal resolution) and the results were compared with lysimeteric data. For this purpose, Landsat 8 and MODIS images were merged in the period of 16 days by Gram-Schmidt method and the actual evapotranspiration of sugarcane was estimated by SEBAL algorithm. In addition, the amount of actual evapotranspiration was calculated using Landsat8 images and SEBAL algorithms. Finally, the results of the two methods were compared with lysimeteric data and were analyzed by statistical methods. The results indicated that the average of absolute difference between actual evapotranspiration of fusion images and lysimeteric method was 0.55 (mm/day). This index was 0.063 (mm/day) for Landsat 8 images compared to lysimeteric data and the average of absolute difference between the two methods of remote sensing was obtained as 0.58 (mm/day). Also at the level of five percent, there is not a significant difference between the two methods of remote sensing.

A system of water governance aims to improve the ecological conditions of resources and their sustainable use. In an era with ecological changes (e.g. extreme events, climate change, etc.), the adaptability of the governance system is so important; therefore, the system capacity of social learning is on the spotlight as the key characteristic. In order to assess the adaptation capacity, the governance system needs to be evaluated with a reference to social learning. Social learning is the learning that occurs by formal and informal institutions based on direct self-experience, observation, and learning from past experiences. Persisting Iran's water resources problems, despite adoption of various policies and laws by Iranian formal water institution, shows that the current institutional structures faces serious weaknesses. This research aimed to apply the social learning loops to evaluate the formal institutional structure of the Iranian water governance in association to the mechanisms governing emergence of water demand in the agricultural sector. Therefore, various documentations including Iran's water laws, national policies and projects related to water and agricultural sectors were evaluated adopting qualitative content analysis and theme analysis methods. The results showed that the formal institution capacity is trapped in a single-loop learning and from this perspective, the formal institution is very vulnerable and suffers from too low adaptation capacity to deal with changes. It was also shown that the governance structure is highly centralized with a dominant top-down hierarchy. In order to enhance the flexibility and adaptability of the water institution, it is necessary to modify the laws associated to the water and agricultural sectors emphasizing on destructive mechanisms. Furthermore, the process of decision-making needs to become participatory engaging all the stakeholders, especially informal institutions. The formal institutions associated to water and agricultural sectors need to get integrated and converge in their policies. Finally, macro-developmental policies require to be redefined with respect to the country’s limiting water resources.

The nonlinear Muskingum model has a significant advantage as compared to the linear model due to the nonlinear relationship between the storage and the flow dishcrage. In this model, the correct estimation of the parameters is necessary to achieve the proper precision. Previous studies indicated that there are five nonlinear corrected models which, with different optimization algorithms, tried to increase the prediction accuracy of output hydrographs. Due to the error in the output hydrograph of the previous models, in this study, a new structure of nonlinear Muskingum model was developed based on hybrid PSO and DSO algorithms. In this eight-parameter model (NL6 model), the improvement coefficient γ was used which held values less or more than one according to the number of peak discharges in the output hydrograph. By applying the proposed approach to the three types of input hydrographs and determining the optimal values of the parameters for the NL6 model, this research showed that the proposed model has a high accuracy in estimating the discharge values of the output hydrograph. The error reduction rate of the NL6 model based on SSQ and SAD indicators for multi-peak hydrographs were 53 and 35.6 percent compared to the last proposed model, respectively. So, this model have a high performance in estimating flood routing hydrograph.

The main objective of this survey was to investigate the influence of extension training programs on knowledge, attitude and behavior of farmers towards water management using theory of planned behavior. Target population included 420 farmers in Zalo-ab rural district in Ravansar in Kermanshah Province who had participated in a couple of extension training programs related to agricultural water conservation, implemented in the region during 2011-2015 time-period. Applying simple random sampling method, 95 farmers were selected according to Cochran formula. Correspondingly 95 farmers were selected using stratified random sampling method from those who had not participated in any extension training programs related to water management. In this way, 190 farmers were included in the study. Data were collected during the second 6-month period in 2015 by a questionnaire validity of which was confirmed by a panel of experts in the fields of agricultural extension and water engineering. Reliability of the questionnaire was approved applying Cronbach Alpha coefficient which was estimated between 0.78 and 0.96 for the scales of the questionnaire. Findings of t-test revealed that farmers, who had participated in extension training programs on water management, have more knowledge, more positive attitude and more appropriate behavior towards agricultural water management. Furthermore, path analysis showed that participation in extension training programs has the highest influence on farmers’ behavior concerning agricultural water conservation. Accordingly, it is recommended to invest more on extension training programs in the region to change attitude, knowledge and behavior of farmers towards agricultural water management.

Institutional adaptability for encountering water shortage has grown slower than changes in process of water resources management. Consequently, the governance structure of the water sector is inefficient in facing new challenges. The institutional gap in the water sector has lead to many problems known as ‘crisis of water governance’. The aim of this study is to assess water institution using “Institutional Development Analysis” (IDA) framework in three levels including laws, policies and administration of the water sector. In addition, the performance of water sector has been evaluated in four dimensions: physical, financial, economic and equity performance. Communication layers of water institution and performance of water sector are presented in form of ‘institution–performance interactions’ model and the simultaneous equations were estimated by the 3SLS method. Theresults showed that the “institution-performance interaction” assessment can provide the strategy for institutional reforms in water governance. The performance of water institution was more dependent on the “effectiveness of water administration” in comparison to the “water law and policy”, which implied that technocratic management plays a central role in water resources management. The performance of water sector was more associated with physical aspects.

In this research the simulation-optimization (S-O) approach is applied to determine the optimum capacity of water transfer systems in “Beheshtabad” to “Zayandehrood” Inter-basin water transfer project. In this regard, a Multi-Objective Multi-Cooperative Swarm Particle Swarm Optimization (MOMCSPSO) algorithm as an optimization technique is linked to Water Evaluation and Planning system (WEAP) as the simulation model. Due to the immense computational efforts of simulation-optimization approach specifically in an evolutionary algorithm application and the need to frequent recalling of the simulation model, intensive computational costs are expected. To alleviate this challenge, a surrogate based S-O approach is developed in this research and the Artificial Neural Network (ANN) as the surrogate model substituted WEAP. The objective functions of the problems were minimizing the environmental and domestic water demand shortages at the origin and destination basins separately while minimizing the costs of the water transfer system. The results showed that the proposed optimization algorithm was able to offer reasonable and diverse solutions withgood functionality in terms of management decisions. Furthermore the developed techniques in this research can effectively reduce the computational time whereas the desired accuracy is achieved in water resources objective function estimations.

The recent drought has raised the significance of water resources planning, maintenance and protection as well as the conservation of local communities. The trend of changes in water resources, particularly those which are limited and response to short-term changes are used in water resources management. In this paper, the pattern of changes in Hamun wetland water body were investigated. This wetland is located in a dry area and therefore the local people are highly dependent on this valuable water resource. As a result of recent drought and the limited water resources, this wetland is experiencing dry periods in one year. Accordingly, the process of filling and drying this wetland were studied for one year. In this regard, Landsat 8 OLI detector data were used to determine the pattern of changes in the water body of Hamun wetland with short intervals. The map of water body and the land use/land cover map were prepared using the hybrid method. Validation showed that this method is accurate enough to produce land use land cover map in areas with diverse land use and land cover. The results of this study showed that Hirmand Hamun retains water in a smaller time period compared to other parts which emphasized the importance of planning for support of the local population in this area. Based on changes detected in Hamun wetland during the inundation period, suitable habitat of water birds is lost during breading season due to water limitation, which can reduce reproductive performance of the water birds. So conservational plans are vital for this wetland.

In this study, distributed Precipitation-Runoff-Modeling-System (PRMS) was used to estimate the spatiotemporal pattern of recharge in Neishaboor Plain in monthly time steps. In this regard, first, it was illustrated based on a sensitivity analysis of PRMS model that the most effective parameters controlling the hydrologic budget components in the study area are evapotranspiration, preferential flow density, waterholding capacity of soil zone, and contributing area in the runoff. Then the calibration of the PRMS was performed using PEST, using runoff in hydrometric stations and actual evapotranspiration (ETEns1.0). The model calibration and validation periods were 7 years (2002-2009) and 2 years (2009-2011), respectively. PRMS calibration based on the two components of the hydrologic budget (runoff and actual ET) led to increase in reliability of calculated recharge. The results revealed that actual ET which was equal to 87 percent of the total rainfall and irrigation water, was the most important component in the hydrologic budget. The second most important component was recharge which covered 12.5 percent of the total rainfall and irrigation water. The PRMS simulation showed that annually 295 MCM of water enters the aquifer as recharge from surface water, most of which occurs in mountains foothill and irrigated areas. This recharge happens from November to the following May. Thus, there is insignificant recharge during the warm months due to the high amount of evapotranspiration and soil water deficit in root zone.

Iran has experienced continuous drought over the past two decades. Different measures have been implemented to respond this situation. The present research was undertaken to evaluate these measures, which can be classified as organizational, operational, research and technology, financial support and relief. The drought management and approaches of the five-year development plans to face water sparsity and drought are also examined. The measures have been evaluated and compared with similar experiences of other countries. The results show that, despite considerable effort, the nation has not been able to institute a relevant structure to cope with water scarcity and, as yet, there is no a national monitoring system. For demand management, the suggested measures have not undergone the necessary evaluation of their capacity to reduce water demand. In fact, some of the objectives for food security are inconsistent those of water security. It appears that the current water governance of country cannot adequately respond to drought and water crises should be expected in the future as a result of increasing water demand and climate change. Policies that address these deficiencies are urgently needed.

Groundwater is known to be a main resource for agricultural, industrial and drinking water. A change in groundwater quality due to wrong groundwater withdrawal management may cause deterioration in other water resources. In this regard the quality assessment and precise monitoring of the groundwater table is of great importance. A proper network for groundwater quality monitoring wells to determine the minimum number of samples on the other hand saves costs. In this research, a method was used based on kriging concept and probability function of normal distribution to evaluate the performance of Mashhad plain's observatory well network. This approach is based on a percentage of region's area criteria with acceptance probability (Ap) accuracy compliance. At first, spatial structure of the sampling wells’ chlorine concentration was extracted using grid semi-variogram and then observation well network was evaluated using algorithm of the acceptance probability method. The results showed that the performance of the existing network or the acceptance accuracy at is 72.1 percent. The results also showed that the accuracy of the observation network using only 35 wells out of 80 wells was the same as the whole network at the probability of 80 percent and the remaining 45 wells had very little impact on the accuracy of the estimation of the spatial variations of chlorine in the aquifer of Mashhad. As a result by performing optimization by the method described for the current network and with displacement or removal of these 45 points, sixteen proposed points increased the acceptance accuracy from %72.1 to %100.

Groundwater is the most important water resource in arid and semiarid area. Therefore, groundwater pollution is also important. In this study, spatial distribution of groundwater quality was evaluated in Shoor River basin in Dehaghan County, south of Esfahan Province. For this propose, kriging, cokriging and IDW methods were used to predict spatial distribution of groundwater quality parameters related to 48 wells and Qanats. According to Anderson Darling test, data of water quality were not normally distributed and therefore COX-BOX transformation was used to normalize the data. Next, the variogram of each parameter was drawn for fitting the best interpolation model. Then, spatial distribution maps of groundwater quality were drawn using ArcGIS. Results showed that ordinary kriging was the best interpolation method for most of the parameters. According to the spatial distribution maps, pollution was aggregated in north of the basin which agreed with the hydrogeological condition in the basin. Also spatial distribution of water quality index (WQI) was determined in the area according to Water Health Organization Standard.

This study investigated the potential of corrosion and scaling for groundwater in the Dezful- Andimeshk plain. Four indicators of Langlier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius scaling Index (PSI), and Larson-Skold Index (LS) were used. For zoning the indicators, this study used the kriging and cokriging methods with fit variograms. According to the results, the Spherical and Gaussian variogram model were best fitting variograms for spatial correlation of indicators. In addition, kriging was the best method for Puckorius and Langlier. For Larson-Skold this was the cokriging method and there was no difference between the methods for the Ryznar index. The groundwater in major part of the Plain was corrosive and in other areas it showed scaling potential. To use the groundwater in this region, provisions should be used; aeration to remove iron and manganese, cathodic protection, lining, and enameling and painting to prevent corrosion and scaling using inhibitors such as phosphate compounds. In addition, reduces extraction from groundwater resources is recommended to reduce the corrosion potential.

Stochastic parametric disaggregation models that maintain spatial and temporal correlation are widely used in hydrology. To avoid high complexity and large number of parameters, which imposes a significant amount of uncertainty to the results, the use of non-parametric disaggregation methods has been widely suggested by researchers as an alternative. Among the non-parametric modeling methods, the K-nearest neighbors method proposed by Prairie et al. gains strong mathematical basis and inherent simplicity. In our work, the modified disaggregation approach of the K-nearest neighbors method is used for temporal and spatial disaggregation of rainfall and river flow values and the method performance is evaluated. The exploited flow and rainfall data corresponded to three stations in three sub-basins located at west of Lake Urmia. The total amount of annual rainfall and flow of the three stations were generated using stochastic lag -1 autoregressive model (AR (1)). Using the non-parametric disaggregation model, the generated annual values were disaggregated into three sub-basins. The annual values for each sub-basin were then disaggregated into different months. Comparing statistics of disaggregated data with those of historical data, showed the good performance of the proposed disagreation model and its ability to disaggregate streamflow and rainfall data.

Low rainfall and subsequent periods with low flow has profound effects on water resource management. In addition, growing water demand would raise critical conditions in periods of severe droughts. Drought management and water use restrictions in one location is a direct function of drought severity. In this paper, we evaluated the duration, severity and index of drought using Herbest method and monthly rainfall deficit forecast values with ANFIS model for 27 stations in the west provinces of Iran in a 30-year period (1985-2014). Drought monitoring results showed that the synoptic stations of Sarab and Kermanshah had the highest and lowest number of dry months; 260 and 122 months, respectively. The maximum relative intensity of drought (Y; dimensionless) were calculated in Maragheh and Jolfa stations as 3.47 and 2.5, respectively. The highest and lowest values of drought index (I) were reached in Takab, Sarab, Saghez and Sar Pol Zahab stations and in stations and Lorestan and Ardabil provinces. The model did not show better performance, except in Kermanshah, Mianeh and Piranshahr stations, in projecting mean monthly rainfall deficits (MMD) using ANFIS model based on the criteria Nash, coefficient of determination, and the error rate.

Nowadays, models as the most important analytical tools, have severely entangled water resources management in rigid structures so that it is hard to consider a water resources problem not using models. This study aimed to use qualitative content analysis method in order to determine the scientific study approach in water resources modeling and investigate the master foresight of each model. Content analysis of published papers in journal of Iran- Water Resources Research from 2005 to 2017 demonstrated that surface water modeling was more concentrated on model assessment for allocation, management and planning, while in groundwater studies, the challenge was on achieving an optimal model for more exploitation of resourses. Investigating modeling objectives showed a discordance in selecting the optimal model that could be due to the nature of the model and the phenomenon under examination. Hence, providing a supermodel is proposed for integration and progression of the outputs of water resources models. The necessities of the supermodel included (a) integrated view to water resources models, (b) complicated nature and climatic status of Iran, (c) pluralistic origins and usages, and (d) institutional complication and multiplicity. The proposed model tried to change the course from “estimate to allocate” to “aim to estimate” in water resources research.