1.
Fazel, Nasim, et al.
(författare)
Regionalization of precipitation characteristics in Iran's Lake Urmia basin
2018
Ingår i: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 132:1-2, s. 363-373
Tidskriftsartikel (refereegranskat) abstract
Lake Urmia in northwest Iran, once one of the largest hypersaline lakes in the world, has shrunk by almost 90% in area and 80% in volume during the last four decades. To improve the understanding of regional differences in water availability throughout the region and to refine the existing information on precipitation variability, this study investigated the spatial pattern of precipitation for the Lake Urmia basin. Daily rainfall time series from 122 precipitation stations with different record lengths were used to extract 15 statistical descriptors comprising 25th percentile, 75th percentile, and coefficient of variation for annual and seasonal total precipitation. Principal component analysis in association with cluster analysis identified three main homogeneous precipitation groups in the lake basin. The first sub-region (group 1) includes stations located in the center and southeast; the second sub-region (group 2) covers mostly northern and northeastern part of the basin, and the third sub-region (group 3) covers the western and southern edges of the basin. Results of principal component (PC) and clustering analyses showed that seasonal precipitation variation is the most important feature controlling the spatial pattern of precipitation in the lake basin. The 25th and 75th percentiles of winter and autumn are the most important variables controlling the spatial pattern of the first rotated principal component explaining about 32% of the total variance. Summer and spring precipitation variations are the most important variables in the second and third rotated principal components, respectively. Seasonal variation in precipitation amount and seasonality are explained by topography and influenced by the lake and westerly winds that are related to the strength of the North Atlantic Oscillation. Despite using incomplete time series with different lengths, the identified sub-regions are physically meaningful.
2.
3.
Baghban, Sahar, et al.
(författare)
Mitigation and Adaptation Measures
2022. - 1
Ingår i: Climate Change in Sustainable Water Resources Management. - Singapore : Springer Nature. - 2364-8198 .- 2364-6934. - 9789811918971 - 9789811918988 ; , s. 331-360
Bokkapitel (refereegranskat) abstract
Climate change has directly and indirectly impacted natural and human systems across the globe in recent decades.
4.
Du, Yiheng, et al.
(författare)
Hydrologic response of climate change in the source region of the Yangtze River, based on water balance analysis
2017
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 9:2
Tidskriftsartikel (refereegranskat) abstract
Due to the large amount of water resources stored in glaciers, permafrost, and lakes, the source region of the Yangtze River (SRYR) is of great importance for the overall basin water flow. For this purpose, a state of art review and calculations were made for the period 1957-2013 using observed hydrological and meteorological data with a water balance approach. Actual evapotranspiration was calculated and validated by empirical formulas. Water storage change analysis was conducted with uncertainty boundaries using a 10-year moving window. Results show that temperature, precipitation, and actual evapotranspiration in the SRYR increased by 0.34°C, 11.4 mm, and 7.6 mm per decade, respectively (significant at 0.05 probability level). Runoffappears to have increased at a rate of 3.3 mm per decade. The SRYR water storage in total has not changed significantly during the period, although the moving average is mostly below zero. Based on the water balance equation, the increase in calculated evapotranspiration is mainly due to the significantly increasing temperature. This in combination with increasing precipitation leads to a relatively stable water storage during the study period. Correlation analyses show that precipitation dominates runoffduring the warm season (May to October), while temperature anomalies dominate the runoffduring the cold season (November to April). The influence of temperature on runoffseems to enhance during the winter period.
5.
du, Yiheng, et al.
(författare)
Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River
2020
Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; 40:4, s. 2285-2295
Tidskriftsartikel (refereegranskat) abstract
Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When out of phase with the SOI, PDO‐induced precipitation anomalies are magnified. When they are in phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.
6.
Hashemi, Hossein, et al.
(författare)
Coupled modeling approach to assess climate change impacts on groundwater recharge and adaptation in arid areas : Coupled modeling approach to assess climate change impacts on groundwater recharge
2015
Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1607-7938. ; 19:10, s. 4165-4181
Tidskriftsartikel (refereegranskat) abstract
The effect of future climate scenarios on surface and groundwater resources was simulated using a model- ing approach for an artificial recharge area in arid southern Iran. Future climate data for the periods of 2010–2030 and 2030–2050 were acquired from the Canadian Global Coupled Model (CGCM 3.1) for scenarios A1B, A2, and B1. These scenarios were adapted to the studied region us- ing the delta-change method. A conceptual rainfall–runoff model (Qbox) was used to simulate runoff in a flash flood prone catchment. The model was calibrated and validated for the period 2002–2011 using daily discharge data. The projected climate variables were used to simulate future runoff. The rainfall–runoff model was then coupled to a calibrated groundwater flow and recharge model (MODFLOW) to simulate future recharge and groundwater hydraulic heads. As a result of the rainfall–runoff modeling, under the B1 scenario the number of floods is projected to slightly increase in the area. This in turn calls for proper management, as this is the only source of fresh water supply in the studied region. The results of the groundwater recharge modeling showed no significant difference between present and future recharge for all scenarios. Owing to that, four abstraction and recharge scenarios were assumed to simulate the groundwater level and recharge amount in the studied aquifer. The results showed that the abstraction scenarios have the most substantial effect on the groundwater level and the continuation of current pumping rate would lead to a groundwater decline by 18 m up to 2050.
7.
Motevalli, Alireza, et al.
(författare)
Inverse method using boosted regression tree and k-nearest neighbor to quantify effects of point and non-point source nitrate pollution in groundwater
2019
Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 228, s. 1248-1263
Tidskriftsartikel (refereegranskat) abstract
Nitrate pollution of groundwater has increased dramatically worldwide due to increase of population and agricultural productivity. The resulting nitrate concentration in groundwater is usually a combination of various types of point and non-point pollutant sources. It is often difficult to distinguish between these sources since groundwater is formed in large and complex catchments with various natural processes and anthropogenic influence that contribute to a certain downstream nitrate concentration. For such conditions, this paper uses a methodology that can be used to inversely determine type and location of main nitrate pollutant source. The methodology builds on two state-of-the-art data mining techniques, boosted regression tree (BRT)and k-nearest neighbor (KNN). These techniques are used to produce a nitrate pollution vulnerability map. The methodology can mitigate effects of subjective judgement on determining importance of different sources and mechanisms for nitrate transport. The investigated mechanisms are hydrogeological, hydrological, anthropogenic, topography, and soil conditioning factors. Thus, the proposed methodology is used to separate between natural processes and anthropogenic effects on nitrate pollution. To calculate the groundwater vulnerability maps, a groundwater nitrate concentration of 40 mg/L (suggested by WHO with a 20% risk margin)was selected as a general threshold for identifying polluted areas that resulted in 96 polluted wells. Non-polluted locations were selected from well data with nitrate concentration less than 15 mg/L (96 non-polluted). The models were trained on 70% polluted and 70% non-polluted site data. The remaining data, 30% polluted and 30% non-polluted sites, were used to validate the simulation results. Results showed that the BRT produced outputs with higher performance than the KNN algorithm. The final ranking results based on the BRT model showed the higher importance of hydraulic conductivity, river density, soil, slope percent, net recharge, and distance from villages, in order, relative to other factors.
8.
Mussabek, Dauren, et al.
(författare)
PFAS in the Drinking Water Source: Analysis of the Contamination Levels, Origin and Emission Rates
2023
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 15:1
Tidskriftsartikel (refereegranskat) abstract
Groundwater contamination caused by the use of the aqueous film-forming foam (AFFF) containing per- and polyfluoroalkyl substances (PFAS) was investigated in southern Sweden. ΣPFAS concentrations in groundwater ranged between 20 and 20,000 ng L−1; PFAS composition was primarily represented by PFOS and PFHxS. The PFAS chain length was suggested to have an impact on the contaminant distribution and transport in the groundwater. PFAS profiling showed that the use of PFSAs- and PFCAs/FTSAs-based PFAS-AFFF can be a contributor to PFAS contamination of the drinking water source (groundwater). PFAS emission was connected to PFAS-AFFF use during the fire-training and fire-fighting equipment tests at the studied location. PFAS emission per individual fire training was (semi-quantitatively) estimated as [1.4 < 11.5 ± 5.7 < 43.7 kg] (n = 20,000). The annual emission estimates varied as [11 < 401 ± 233 < 1125 kg yr−1] (n = 1005) considering possible [2 < 35 ± 20 < 96] individual fire-training sessions per year.
9.
Mussabek, Dauren, et al.
(författare)
Temporal trends and sediment–water partitioning of per- and polyfluoroalkyl substances (PFAS)in lake sediment
2019
Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 227, s. 624-629
Tidskriftsartikel (refereegranskat) abstract
The use of per- and polyfluoroalkyl substances (PFAS)containing aqueous film forming foams (AFFF)at fire training facilities can have an adverse impact on the surrounding environment. The aim of the present study was to study the distribution and temporal trend of 26 PFAS in water and sediment cores for a lake and a pond affected by AFFF release from a fire training facility in Luleå, northern Sweden. In the aqueous phase, maximum ΣPFAS concentration was 1.700 ± 90 ng L −1 . Dominant PFAS groups were perfluoroalkane sulfonates (PFSAs)with 70% of the ΣPFAS, followed by perfluoroalkyl carboxylates (PFCAs, 29%), whereas the contribution of 6:2 fluorotelomer carboxylate (FTSAs)was low (<1%). In the sediment core samples, ΣPFAS concentrations ranged between <1 μg kg −1 dry weight (dw)and 76 μg kg −1 dw, where perfluorooctane sulfonate (PFOS)and perfluorohexane sulfonate (PFHxS)had an average contribution of ∼71% and ∼23% of the ΣPFAS. The sediment core analysis indicated that the PFAS contamination began about 1994 and the highest accumulation rate was observed for the period 2003–2009. The PFAS flux increased from 2.3 μg m −2 yr −1 dw in 1994 to 12 μg m −2 yr −1 dw by 2009. Over the accumulation period 1994–2009, the lake sediment surface received 213 μg m −2 dw for ƩPFAS, where PFOS contributed with 125 μg m −2 yr −1 dw and PFHxS with 65 μg m −2 dw. Results point to that sediment cores collected near PFAS hotspot areas can be used as a contamination record to reconstruct release history.
10.
Nakagawa, Kei, et al.
(författare)
Modeling of Salt Sorption in Volcanic Ash Soil
2017
Ingår i: Communications in Soil Science and Plant Analysis. - : Informa UK Limited. - 0010-3624 .- 1532-2416. ; 48:21, s. 2594-2600
Tidskriftsartikel (refereegranskat) abstract
Groundwater pollution by nitrate from agricultural fields is a worldwide problem. To improve the understanding of nitrate transport processes through volcanic ash soils overlying groundwater aquifers, salt sorption experiments were performed. Salt sorption is the process that involves the simultaneous use of cation and anion adsorption mechanisms without changing the pH. Prepared six different concentrations of potassium chloride (KCl) solutions were mixed with soil samples. Anion and cation contents of the liquid and solid phases were determined. Experiments were performed in triplicate of six kinds of KCl solutions for three types of soils. Thus, total 54 of samples were analyzed. Relationships between ionic strength and sorption capacity increments of cations and anions were determined. The results show that if ionic strength of the infiltrating solution to the volcanic ash soil is known, the ECEC (effective cation exchange capacity) and EAEC (effective anion exchange capacity) can be reliably estimated. The resulting prediction equations can be included to improve reactive transport simulation models. Consequently, it will be possible to better understand solute transport with changing sorption capacity for the solid soil phase.
