1.
Cantoni, Jacopo, et al.
(författare)
Legacy contributions to diffuse water pollution : Data-driven multi-catchment quantification for nutrients and carbon
2023
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 879, s. 163092-
Tidskriftsartikel (refereegranskat) abstract
Legacy pollutants are increasingly proposed as possible reasons for widespread failures to improve water quality, de -spite the implementation of stricter regulations and mitigation measures. This study investigates this possibility, using multi-catchment data and relatively simple, yet mechanistically-based, source distinction relationships between water discharges and chemical concentrations and loads. The relationships are tested and supported by the available catch -ment data. They show dominant legacy contributions for total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC) across catchment locations and scales, from local to country-wide around Sweden. Consistently across the study catchments, close relationships are found between the legacy concentrations of TN and TOC and the land shares of agriculture and of the sum of agriculture and forests, respectively. The legacy distinction and quantification capabilities provided by the data-driven approach of this study could guide more effective pollution mitigation and should be tested in further research for other chemicals and various sites around the world.
2.
Dehghanipour, Mohammad Hassan, et al.
(författare)
Two Comprehensive and Practical Methods for Simulating Pan Evaporation under Different Climatic Conditions in Iran
2021
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13:20
Tidskriftsartikel (refereegranskat) abstract
Evaporation from surface water plays a crucial role in water accounting of basins, water resource management, and irrigation systems management. As such, the simulation of evaporation with high accuracy is very important. In this study, two methods for simulating pan evaporation under different climatic conditions in Iran were developed. In the first method, six experimental relationships (linear, quadratic, and cubic, with two input combinations) were determined for Iran's six climate types, inspired by a multilayer perceptron neural network (MLP-NN) neuron and optimized with the genetic algorithm. The best relationship of the six was selected for each climate type, and the results were presented in a three-dimensional graph. The best overall relationship obtained in the first method was used as the basic relationship in the second method, and climatic correction coefficients were determined for other climate types using the genetic algorithm optimization model. Finally, the accuracy of the two methods was validated using data from 32 synoptic weather stations throughout Iran. For the first method, error tolerance diagrams and statistical coefficients showed that a quadratic experimental relationship performed best under all climatic conditions. To simplify the method, two graphs were created based on the quadratic relationship for the different climate types, with the axes of the graphs showing relative humidity and temperature, and with pan evaporation, were drawn as contours. For the second method, the quadratic relationship for semi-dry conditions was selected as the basic relationship. The estimated climatic correction coefficients for other climate types lay between 0.8 and 1 for dry, semi-dry, semi-humid, Mediterranean climates, and between 0.4 and 0.6 for humid and very humid climates, indicating that one single relationship cannot be used to simulate pan evaporation for all climatic conditions in Iran. The validation results confirmed the accuracy of the two methods in simulating pan evaporation under different climatic conditions in Iran.
3.
Destouni, Georgia, et al.
(författare)
Distinguishing active and legacy source contributions to stream water quality : Comparative quantification for chloride and metals
2021
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 35:7
Tidskriftsartikel (refereegranskat) abstract
Hydrochemical constituents in streams may originate from currently active sources at the surface and/or legacy sources from earlier surface inputs, waste deposits and land contamination. Distinction and quantification of these source contributions are needed for improved interpretation of tracer data and effective reduction of waterborne environmental pollutants. This article develops a methodology that recognizes and quantifies some general mechanistic differences in stream concentration and load behavior versus discharge between such source contributions. The methodology is applied to comparative analysis of stream concentration data for chloride (Cl-), copper (Cu), lead (Pb), and zinc (Zn), and corresponding data for water discharge, measured over the period 1990-2018 in multiple hydrological catchments (19 for Cl-, 11 for Cu and Zn, 10 for Pb) around the major Lake Malaren in Sweden. For Cl-, the average load fraction of active sources is quantified to be 19%, and the average active and legacy concentration contributions as 2.9 and 11 mg/L, respectively. For the metals, the average active load fractions at outlets are 1%-3% over all catchments and 9%-14% in the relatively few catchments with mixed metal sources. Average active and legacy concentration contributions are 0.14 and 3.2 mu g/L for Cu, 0.05 and 1.5 mu g/L for Pb, and 1.4 and 12 mu g/L for Zn, respectively. This multi-catchment analysis thus indicates a widespread prevalence of legacy sources, with greater legacy than active concentration contributions for both Cl- and the metals, and active contributions playing a greater role for chloride than for the metals. The relatively simple first-order methodology developed and applied in the study can be used to screen commonly available stream monitoring data for possible distinction of active and legacy contributions of any hydrochemical constituent in and across various hydrological catchment settings.
4.
Kalantari, Zahra, et al.
(författare)
Modeller subjectivity and calibration impacts on hydrological model applications : an event-based comparison for a road-adjacent catchment in South-East Norway
2015
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 502, s. 315-329
Tidskriftsartikel (refereegranskat) abstract
Identifying a ‘best’ performing hydrologic model in a practical sense is difficult due to the potential influences of modeller subjectivity on, for example, calibration procedure and parameter selection. This is especially true for model applications at the event scale where the prevailing catchment conditions can have a strong impact on apparent model performance and suitability. In this study, two lumped models (CoupModel and HBV) and two physically-based distributed models (LISEM and MIKE SHE) were applied to a small catchment upstream of a road in south-eastern Norway. All models were calibrated to a single event representing typical winter conditions in the region and then applied to various other winter events to investigate the potential impact of calibration period and methodology on model performance. Peak flow and event-based hydrographs were simulated differently by all models leading to differences in apparent model performance under this application. In this case-study, the lumped models appeared to be better suited for hydrological events that differed from the calibration event (i.e., events when runoff was generated from rain on non-frozen soils rather than from rain and snowmelt on frozen soil) while the more physical-based approaches appeared better suited during snowmelt and frozen soil conditions more consistent with the event-specific calibration. This was due to the combination of variations in subsurface conditions over the eight events considered, the subsequent ability of the models to represent the impact of the conditions (particularly when subsurface conditions varied greatly from the calibration event), and the different approaches adopted to calibrate the models. These results indicate that hydrologic models may not only need to be selected on a case-by-case basis but also have their performance evaluated on an application-by-application basis since how a model is applied can be equally important as inherent model structure.
5.
Khazaei, Bahram, et al.
(författare)
Climatic or regionally induced by humans? Tracing hydro-climatic and land-use changes to better understand the Lake Urmia tragedy
2019
Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 569, s. 203-217
Tidskriftsartikel (refereegranskat) abstract
Lake Urmia-a shallow endemic hypersaline lake in northwest Iran-has undergone a dramatic decline in its water level (WL), by about 8 m, since 1995. The primary cause of the WL decline in Lake Urmia has been debated in the scientific literature, regarding whether it has been predominantly driven by atmospheric climate change or by human activities in the watershed landscape. Using available climate, hydrological, and vegetation data for the period 1981-2015, this study analyzes and aims to explain the lake desiccation based on other observed hydro-climatic and vegetation changes in the Lake Urmia watershed and classical exploratory statistical methods. The analysis accounts for the relationships between atmospheric climate change (precipitation P, temperature T), and hydrological (soil moisture SM, and WL) and vegetation cover (VC; including agricultural crops and other vegetation) changes in the landscape. Results show that P, T, and SM changes cannot explain the sharp decline in lake WL since 2000. Instead, the agricultural increase of VC in the watershed correlates well with the lake WL change, indicating this human-driven VC and associated irrigation expansion as the dominant human driver of the Lake Urmia desiccation. Specifically, the greater transpiration from the expanded and increasingly irrigated agricultural crops implies increased total evapotranspiration and associated consumptive use of water (inherently related to the irrigation and water diversion and storage developments in the watershed). Thereby the runoff from the watershed into the lake has decreased, and the remaining smaller inflow to the lake has been insufficient for keeping up the previous lake WL, causing the observed WL drop to current conditions.
6.
Bemmoussat, A., et al.
(författare)
Contribution of Satellite-Based Precipitation in Hydrological Rainfall–Runoff Modeling : Case Study of the Hammam Boughrara Region in Algeria
2021
Ingår i: Earth Systems and Environment. - : Springer Nature. - 2509-9426 .- 2509-9434. ; 5:4, s. 873-881
Tidskriftsartikel (refereegranskat) abstract
Hydrological models are viewed as powerful tools that have a major importance for managing water resources and predicting flows. It should be specified that the meteorological parameter rainfall is the main input in these models. In the current study, data from only one rainfall station are available over the analysis domain, which cannot represent the entire Hammam Boughrara watershed of Algeria. The precipitation data remotely detected by the tropical rainfall measuring mission (TRMM) provide good spatial coverage in the watershed and can be used to fill in the missing data. The use of raw TRMM data gives poor results from the simulated flow rates with a Nash–Sutcliffe efficiency NSE equal to 0.34 for the validation period that ranges from year 2000 to 2005; this is mainly due to uncertainties in the TRMM data. For this reason, it was deemed necessary to carry out a performance test of the model. The results obtained give an unsatisfactory percent bias (PBIAS) of − 46.24%, which suggests the need to perform a correction to decrease the PBIAS of satellite precipitation. For this, two methods were used: the linear regression method and the multiplicative method. These two techniques can only be applied if there is at least one rainfall measurement station available in the watershed. The obtained results are very satisfactory since the PBIAS reaches − 0.62% for the linear regression method and − 11.58% for the multiplicative method. In addition, the use of corrected TRMMs gives also very good results with a Nash–Sutcliffe efficiency that ranges from 0.74 to 0.88 for both validation and calibration periods. Overall, the current study is supportive to estimate the satellite-based rainfall, one of the very sensitive to measure the meteorological parameter, in northwestern Algeria.
7.
Blösch, Günter, et al.
(författare)
Twenty-three unsolved problems in hydrology (UPH) - a community perspective
2019
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
Tidskriftsartikel (refereegranskat) abstract
This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
8.
Boulet, Anne-Karine, et al.
(författare)
Hydrological Processes in Eucalypt and Pine Forested Headwater Catchments within Mediterranean Region
2021
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13:10
Tidskriftsartikel (refereegranskat) abstract
Mediterranean headwater catchments have experienced major land-use changes in recent centuries, namely characterized by afforestation with fast-growing tree species (e.g., pine and eucalyptus). This paper investigates differences in the hydrological response of two forested catchments with distinct Pinus pinaster Aiton (PIN) and Eucalyptus globulus Labill. (EUC) covers over 6 hydrological years, from 2010 to 2016. The study was developed in paired catchments located in North-Central Portugal, under wet Mediterranean climate and schist bedrock. Based on rainfall and streamflow measurements, the hydrological responses were analyzed through the water-balance calculations, rainfall-runoff event analyses, and correlations between rainfall characteristics, evapotranspiration, soil moisture, overland flow, and land-cover parameters. The study period recorded a wide range of annual rainfall, between 984 and 2127 mm per years. The annual streamflow displayed greater inter-annual variation, from 208 to 1430 mm for PIN and from 217 to 1291 mm for EUC. The runoff coefficient was higher in the wettest years, with a maximum of 58% for PIN and 61% for EUC, and decreased substantially in the driest year, representing only 17% of the rainfall in PIN and 22% in EUC. Rainfall was predominant during the winter season (41%), followed by autumn (30%) and spring (24%). The streamflow displayed a seasonal behavior in both catchments, with higher runoff coefficient for EUC that for PIN. Half of the annual streamflow occurs during the winter, with the highest average runoff coefficient attained for EUC and PIN respectively being 68% and 64% of the rainfall amount. Annual evapotranspiration was relatively constant through the six years of study and showed higher average values in PIN (907 mm) than EUC (739 mm), highlighting the importance of forest type and showing that mature pine plantations lead to higher water consumption than eucalypt stands. Annual rainfall amount affects evapotranspiration rate (%), the percentage of ET increasing from 37% to 78% for PIN and from 34% to 73% for EUC between the wettest and the driest years, which raises concerns regarding the impact of climate changes on water availability in the mountain areas of the Mediterranean region.
9.
Darabi, H., et al.
(författare)
Development of a novel hybrid multi-boosting neural network model for spatial prediction of urban flood
2021
Ingår i: Geocarto International. - : Taylor and Francis Ltd.. - 1010-6049 .- 1752-0762.
Tidskriftsartikel (refereegranskat) abstract
In this study, a new hybridized machine learning algorithm for urban flood susceptibility mapping, named MultiB-MLPNN, was developed using a multi-boosting technique and MLPNN. The model was tested in Amol City, Iran, a data-scarce city in an ungauged area which is prone to severe flood inundation events and currently lacks flood prevention infrastructure. Performance of the hybridized model was compared with that of a standalone MLPNN model, random forest and boosted regression trees. Area under the curve, efficiency, true skill statistic, Matthews correlation coefficient, misclassification rate, sensitivity and specificity were used to evaluate model performance. In validation, the MultiB-MLPNN model showed the best predictive performance. The hybridized MultiB-MLPNN model is thus useful for generating realistic flood susceptibility maps for data-scarce urban areas. The maps can be used to develop risk-reduction measures to protect urban areas from devastating floods, particularly where available data are insufficient to support physically based hydrological or hydraulic models.
10.
Ghajarnia, Navid, et al.
(författare)
Data-Driven Worldwide Quantification of Large-Scale Hydroclimatic Covariation Patterns and Comparison With Reanalysis and Earth System Modeling
2021
Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:10
Tidskriftsartikel (refereegranskat) abstract
Large-scale covariations of freshwater fluxes and storages on land can critically regulate the balance of green (evapotranspiration) and blue (runoff) water fluxes, and related land-atmosphere interactions and hydroclimatic hazards. Such large-scale covariation patterns are not evident from smaller-scale hydrological studies that have been most common so far, and remain largely unknown for various regions and climates around the world. To contribute to bridging the large-scale knowledge gaps, we synthesize and decipher hydroclimatic data time series over the period 1980-2010 for 6,405 catchments around the world. From observation-based data, we identify dominant large-scale linear covariation patterns between monthly freshwater fluxes and soil moisture (SM) for different world parts and climates. These covariation patterns are also compared with those obtained from reanalysis products and Earth System Models (ESMs). The observation-based data sets robustly show the strongest large-scale hydrological relationship to be that between SM and runoff (R), consistently across the study catchments and their different climate characteristics. This predominantly strongest covariation between monthly SM and R is also the most misrepresented by ESMs and reanalysis products, followed by that between monthly precipitation and R. Comparison of observation-based and ESM results also shows that an ESM may perform well for individual monthly variables, but fail in representing the patterns of large-scale linear covariations between them. Observation-based quantification of these patterns, and ESM and reanalysis improvements for their representation are essential for fundamental understanding, and more accurate and reliable modeling and projection of large-scale hydrological conditions and changes under ongoing global and regional change.
