Groundwater Assessment at Santiago Island (Cabo Verde): A Multidisciplinary Approach to a Recurring Source of Water Supply

Groundwater resources are in many parts of the world the only source for private domestic, agricultural and public water supply. Subsurface has also become major recipient of wastewater and solid waters especially in the developing countries. Overexploitation of coastal aquifers and pollution are among the main problems related to groundwater resources assessment and management in Santiago Island (Cabo Verde). Brackish groundwater is the only available water type in the region that is being provided to numerous parts of the Island such as Praia Baixo, Montenegro, and Charco for agriculture and human supply. Solute and isotope data obtained in different groundwater systems were used in the identification of groundwater resources degradation. In order to understand the influence of the anthropogenic activities on the water quality and the main origin of the salts in groundwater, a statistical approach (Principal Components Analyses—PCA) was performed on the physico-chemical data. The results obtained indicate water–rock interaction mechanisms as the major process responsible for the groundwater quality (mainly calcium-bicarbonate type), reflecting the lithological composition of the subsurface soil. Also, anthropogenic contamination was identified, in several points of the island. Isotopic techniques (δ²H, δ¹⁸O and ³H content) combined with geochemistry provided comprehensive information on groundwater recharge, as well as on the identification of salinization mechanisms (e.g. seawater intrusion, salt dissolution, and marine aerosols) of the groundwater systems, at Santiago Island.     

Water quality assessment and apportionment source of pollution from neighbouring rivers in the Tapeng Lagoon (Taiwan) using multivariate analysis: a case study.

Factor analysis was conducted to explain the characteristics and variation in the quality of water during the disassembly of oyster frames and fishery boxes. The result shows that the most important latent factors in the Tapeng Lagoon are the ocean factor, the primary productivity factor, and the fishery pollution factor. Canonical discriminant analysis is applied to identify the source of pollution in neighbouring rivers outside the Tapeng Lagoon. The two constructed discriminant functions (CDFs) showed a marked contribution to all the discriminant variables, and that total nitrogen, algae, dissolved oxygen, and total phosphate combined in the nutrient effect factor. The recognition capacities in these two CDFs were 95.6% and 4.4%, respectively. The water quality in the Kaoping river most strongly affected the water quality in the Tapeng Lagoon. Disassembling the oyster frames and fishery boxes improved the water quality markedly. However, environmental topographic conditions indicate that strengthening stream pollution prevention and constructing another entrance to the ocean are the best approaches for improving the quality of water in the Tapeng Lagoon by reducing eutrophication. These approaches and results yield useful information concerning habitat recovery and water resource management.     

不同水质评价方法的应用比较研究——以丹江口水库入库河流为例

为准确了解丹江口水库直接入库河流水质状况及其主要污染因子,基于2015年16条入库河流河口水质监测成果,分别采用单因子评价法、综合污染指数法和主成分分析法对水质进行评价。3种评价方法均得出神定河、泗河和犟河水质较差的结论;筛选出的主要污染因子大致相同,为总氮、高锰酸盐指数、五日生化需氧量、氨氮和总磷;不同评价方法对河流水质状况评价结果和污染因子排序略有不同,单因子评价法只能给出评价类别,综合污染指数法和主成分分析法适用于不同时空的水质变化比较。结合当前丹江口库区水质管理工作,建议适当调整泗河、神定河、犟河水质管理目标,除水质类别外,建议增加主要污染因子的消减目标。     

The Role of Green Roofs as a Source/sink of Pollutants in Storm Water Outflows

Green roofs are increasingly used as sustainable urban drainage systems due to their retention and detention capacity; however, the impact of green roofs in term of water quality is still a debated issue among researchers. A monitoring programme was carried out at the University of Genoa on a full-scale experimental site to assess the quality of storm water outflows. As for rainfall, the bulk deposition (dry and wet fractions) is collected to evaluate the role of the overall atmospheric deposition in altering storm water quality. The pollutant load observed in the green roof outflow is limited; concentration values for solids and metals are lower than those generally observed in storm water runoff from impervious surfaces. Suspended solids and Chemical Oxygen Demand (COD) are below respectively 10 and 20 mg/l, on average; as for heavy metals, copper and zinc are equal to 30 μg/l on average, while iron is equal to 120 μg/l. The Event Mean Concentration (EMC) statistics of the pollutant loads associated with the rainfall and outflow have been compared and discussed. The observed green roof behaviour as a sink/source of pollutants with respect to the atmospheric deposition is also investigated based on both concentration and mass. Results demonstrate that: green roof behaves as a source with respect to solids, COD and potassium while zinc and mainly copper are retained within the green roof stratigraphy. The resulting mass delivery behaviour reveals that no significant first flush occurs for pollutant constituents irrespective of the hydrologic characteristics and pollutant sources.     

Discharge pulses of hydroelectric dams and their effects in the downstream limnological conditions: a case study in a large tropical river (SE Brazil)

To address daily fluctuations in electricity demands, the quantities of water passing through the turbines of hydropower plants can vary significantly (up to fourfold) during a 24‐h cycle. This study evaluates the effects of hourly variations in water discharges on the limnological conditions observed in two below‐dam river stretches. The study reservoirs, Capivara and Taquaruçu, are the 9th and 10th reservoirs in a cascade of dams in the Paranapanema River in south‐east Brazil. The reservoirs exhibit different trophic conditions, water retention times, thermal regimes and spillway positions. Capivara Reservoir is deeper, meso‐eutrophic, with a high water retention time and hypolimnetic discharges (32 m) varying between 500 and 1400 m³ s^?1. In contrast, Taquaruçu Reservoir is relatively shallow, oligo‐mesotrophic, and has a low retention time, with water discharges varying between 500 and 2000 m³ s^?1. Its turbine water intake zone also is more superficial (7 m). For two periods of the year, winter and summer, profiles of limnological measurements were developed in the lacustrine (above‐dam site) zones of the reservoirs, as well as in the downstream river stretches (below‐dam site). In both cases, the sampling was carried out at 4‐h intervals over a complete nictemeral cycle. The results demonstrated that the reservoir operating regime (water discharge variations) promoted significant differences in the conditions of the river below the dams, especially for water velocity, turbidity, and nutrient and suspended solids concentrations. The reservoir physical characteristics, including depth, thermal stratification and outlet structure, are also key factors influencing the limnology and water quality at the below‐dam sampling sites. In the case of Capivara Reservoir, for example, the low dissolved oxygen concentration (<5.0 mg L^?1) in its bottom water layer was transferred to the downstream river stretches during the summer. These study results demonstrated that it is important to continue such investigations as a means of verifying whether or not these high‐amplitude/low‐frequency variations could negatively affect the downstream river biota.     

Groundwater use in Spain: an overview in light of the EU Water Framework Directive

In semi-arid regions, aquifers provide a series of practical advantages that make them preferential sources of water supply. In Spain, groundwater meets about one-fifth of the total water demand and is used to irrigate over one-third of the total irrigated land. This article examines groundwater use in Spain from the perspective of the EU Water Framework Directive. Analysis of different sector uses suggests that core problems (and solutions) related to groundwater lie in agricultural uses and that the Directive's environmental requirements remain distant from reality on the ground, where economic, political and social reasons prevail on legal obligations set by national and supranational authorities.     

Machine-learning modeling of hourly potential thermal refuge area: A case study from the Sainte-Marguerite River (Quebec,Canada)

To understand the temporal and spatial variability of thermal refuges, this study focused on modeling potential thermal refuge area (PTRA) at a sub-daily time-step in two tributary confluences of the Sainte-Marguerite River (Canada) during the summers of 2020 and 2021. Aquatic ectotherm species, such as Atlantic salmon (Salmo salar), seek these refuges to avoid heat stress during high summer river temperatures. To investigate the temporal variability of these PTRA, we employed inverse weighted distance interpolation to delineate the hourly area available at both confluences. We then analyzed the impact of the atypical low flow conditions of summer 2021 on the diel cycle of PTRA extremes using the coefficient of variation and the generalized additive model (GAM). Finally, we used four supervised machine-learning regression models and three to five hydrometeorological predictors to estimate hourly PTRA availability: multivariate adaptive splines regression (MARS), GAM, support vector machine regression (SVM), and random forest regression (RF). The results showed that tree-based and kernel-based regression models, RF and SVM, outperformed GAM and MARS. RF had the highest accuracy at both sites, with a relative root mean square error and Nash–Sutcliffe efficiency coefficient (Nash) of 13% and 93%, respectively. Our study discovered that under warm conditions in August 2021, small perennial tributary inflows in combination with low mainstem discharge could create high and constant PTRA at confluences, potentially providing vital thermal refuges for cold-water taxa. These refuges may be especially important at the local level, within a specific stretch or section of the river. Given the decreasing availability of thermal refuges for salmonids, it is crucial to monitor stream temperatures at small spatial and temporal scales using data-driven techniques in order to understand stream temperature heterogeneity at tributary confluences.     

Quagga mussels (Dreissena bugensis) as biomonitors of metal contamination: A case study in the upper St. Lawrence River

In this study, the utility of quagga mussels (Dreissena bugensis) as biomonitors was investigated by measuring total concentrations of three trace metals, cadmium, copper, and zinc, in soft tissues. Quagga mussels were sampled from five sites along the upper St. Lawrence River, including one industrially influenced site, from 1999 through 2007. Mussels were collected from near-shore areas, divided into 5 size classes based on maximum shell length, and tissues were pooled for analysis of each size group. Two-way analysis of variance and a posteriori range tests were used to test for differences among sites along a distance gradient from the outflow of Lake Ontario and to examine inter-annual variability within and among sites. Cadmium concentrations were higher nearer the outflow of the lake. Copper concentrations varied among sites and years, but were generally highest near the industrial site. Zinc concentrations were relatively uniform, possibly reflecting internal regulation. Animal size measured as shell length was not an important factor in this section of the river, but warrants further consideration in a wider range of ecosystems and contaminant exposure levels. In general, concentrations of the three metals were not high compared to reports in the published literature for dreissenid mussels in contaminated environments. However, few studies have utilized quagga mussels rather than zebra mussels. The two species may differ in bioaccumulation patterns and may not be interchangeable as biomonitors. Further studies of bioaccumulation of contaminants by quagga mussels in a wider range of contaminant exposures would be useful particularly as quagga mussels displace zebra mussels in the Laurentian Great Lakes and the St. Lawrence River.     

Planktonic indicators of water quality: A case study in the Amacuzac River Basin (State of Morelos,Mexico)

Planktonic organisms are good indicators of water quality but are rarely used in Mexican riverine studies in spite of the high level of contamination in these lotic waters. In this study, we focused on the plankton of the river Amacuzac in Mexico and a large saline waterbody, Lake Tequisquitengo, which is located in the Amacuzac river basin. We collected samples at three sites in the River Amacuzac and one at Lake Tequisquitengo from May 2015 to March–April of 2016. We analysed the physicochemical variables, coliform bacteria, and biological oxygen demand levels. We also quantified phytoplankton and zooplankton. Our results indicate that the study sites are mesotrophic with high densities of diatoms and cyanobacteria. Among the zooplankton, the dominant organisms were rotifers. The constancy of planktonic taxa was high in the lake but low in the river. The Descy index ranged from 2.9 to 4.5 in the river and from 4.0 to 5.0 in the lake. The saprobic index shows that the system is β‐mesosaprobic. The species diversity was higher in the river than in the lake. Our study shows that plankton can efficiently be used to evaluate the water quality in rivers and lakes.     

基于标准水资源指数(SWRI)的流域水文干旱评估——以海河北系为例

构建了一个新的水文干旱评估指标——标准水资源指数(SWRI),结合分布式水循环模型、Copula函数及统计检验等方法,形成了一套完整的水文干旱识别、评估及特征分析的基本框架。以海河北系为例,定量识别了1956—2009年间的水文干旱事件,并对其干旱特征及变化规律进行了剖析。结果表明:海河北系近54年发生的34次水文干旱主要集中在短历时、低强度、小面积区间内,空间上主要分布在张家口、大同及北京等地区;干旱指标的联动关系上,干旱历时、强度与面积指标间呈显著的线性或指数相关关系,90%的水文干旱历时低于40个月、干旱面积占比不超过43%,干旱强度低于9.0;在给定的干旱特征指标值(如干旱面积)条件下,另一干旱指标值越大(如强度越大)干旱发生概率越小,且存在明显的特征区间;单变量水文干旱重现期介于联合重现期和同现重现期之间。     

Ecosystem-based management in challenging conditions: implications of a case study from north-eastern Turkey

This paper studies ways to implement ecosystem-based management (EBM) regardless of data and governance conditions. It focuses on a case study from Turkey and considers how EBM can be implemented under certain specific challenging conditions. The case study provides conceptual context diagrams of actual and hypothetical situations and then compares them using soft systems methodology. This comparison emphasizes the need for a firm political will that fully enforces regulations on the protection of water resources. The paper also recommends a productive stakeholder engagement that empowers locals and uses local knowledge to meet information requirements for progress towards EBM implementation under challenging conditions.     

水动力模型的地形前处理方法研究——以辽河铁岭段为例

随着科技发展,水利工作走向了数字化时代。使用计算机软件构建数学模型可以方便快捷地对水力情况进行模拟,而研究区地形的提取是构建数学模型的基础。本文介绍了常用的地形前处理方法,并结合实际工作诠释了地形提取的过程。     

Groundwater contributions to surface water in the Assiniboine Delta Aquifer (ADA): A water quantity and quality perspective

In the Lake Winnipeg Basin (LWB), at both basin and regional scales, there are currently gaps regarding the significance of groundwater as a mediator of nutrient and contaminant fluxes to Lake Winnipeg. During 2018, surface water and groundwater samples were collected from various locations across the largest sand and gravel aquifer (Assiniboine Delta Aquifer [ADA]; 3800 km²) in the LWB as well as from surface water courses flowing above this aquifer. The samples collected during spring and fall were analyzed for anions and cations as well as for a series of isotopic and geochemical tracers (e.g. water isotopes, carbon 14, artificial sweeteners, pesticides, etc.). The results reveal that groundwater and the small watercourses flowing above the ADA have a similar chemical composition, which is in contrast with the chemical composition of the main watercourse flowing above the aquifer (Assiniboine River [AR]). When corroborated with stream discharge measurements this indicates that groundwater plays a significant role at local scale in controlling both the flow and the chemical composition of the AR tributaries. Nitrate showed low to non-detectable concentrations in both groundwater and surface water. With respect to groundwater, this could be related to the reducing conditions in the deeper aquifer in conjunction with relatively large groundwater travel times of up to 2400 years.     

Water quality in the southern Tibetan Plateau: chemical evaluation of the Yarlung Tsangpo (Brahmaputra)

Yarlung Tsangpo (Brahmaputra) is the largest river system draining the northern slopes of the Himalayan ranges on the southern Tibetan Plateau. It remains one of only two large non‐regulated rivers in China. In this paper the chemical composition of Yarlung Tsangpo and its major tributaries (Raga Tsangpo, Nyangchu and Lhasa River) are studied. Water samples (n = 55) were collected and measured for major ions, trace elements and nutrients in order to: (1) define the present chemical quality of this water course; (2) address possible mechanisms governing the water chemical compositions, and (3) identify potential sources for contaminants. Multivariable analysis shows that geology and climate are the major explanatory variables for the spatial variation in water chemistry in this river system. In general, water chemistry is mainly controlled by carbonate weathering, with Ca²⁺ and HCO being the dominant ions. In addition, runoff from brackish/saline lakes and geothermal waters, enriched in Na⁺, Cl^?, SO, Mg²⁺ and Li, are major contributors of elevated concentrations of these solutes in the headwater regions resulting in a relatively high loading of total dissolved solids (TDS, 146–397 mg L^?1). Levels of most heavy metals and total dissolved nutrients were generally found to be low. However, elevated As concentration (avg. 95 μg L^?1) in the headwaters and additions from untreated wastewater were evident at some locations. Copyright © 2009 John Wiley & Sons, Ltd.     

GM(0,N)模型在湿地面积预测中的应用——以莫莫格湿地为例

预测未来年度湿地面积,对研究湿地生境变化趋势、保护湿地有重要作用。建立灰度GM(0,N)模型旨在提供一种简便的方法,预测湿地水面面积大小。首先应用灰色关联度分析模型,量化确定了对湿地面积影响程度较大的相关因素,分别是:莫莫格湿地年降水量、嫩江径流量、洮儿河径流量。利用这三个相关因素建立了GM(0,N)预测模型,对莫莫格湿地面积进行了模拟预测。为了提高精度,对GM(0,N)模型进行了修正。利用残差和后验差检验方法对模型作了可靠度分析,检测结果显示:修正的GM(0,N)模型平均相对误差9.1%,后验差检验等级为1级,多元线性回归模型平均相对误差15.5%,说明灰度预测模型对于莫莫格湿地水面面积预测具有一定优势。     

Conjunctive Use of Surface Water and Groundwater: Application of Support Vector Machines (SVMs) and Genetic Algorithms

Combined simulation-optimization models have been widely used to address the management of water resources issues. This paper presents a simulation-optimization model for conjunctive use of surface water and groundwater at a basin-wide scale, the Zayandehrood river basin in west central Iran. In the Zayandehrood basin, in the past 10 years, a historical low rainfall in the head of the basin, combined with growing demand for water, has triggered great changes in water management at basin and irrigation system level. The conjunctive use model that coupled numerical simulation with nonlinear optimization is used to minimize shortages of water in meeting irrigation demands for four irrigation systems. Constraints guarantee the maximum/minimum cumulative groundwater drawdown and maximum capacity of irrigation systems. A support vector machines (SVMs) model is developed as a simulator of surface water and groundwater interaction model while a genetic algorithm (GA) is used as the optimization model. Conjunctive use model runs for three scenarios. Results show that the accuracy of SVMs as a simulator for surface water and groundwater interaction model is good and that it is possible to decrease the water shortage for irrigation systems with application of proposed SVMs-GA model.     

Water reuse in the Apatlaco River Basin (México): a feasibility study.

The aim of this work is to determine the technical and economic feasibility of implementing different reclamation and reuse projects that improve the quality of the Apatlaco river basin located in the central part of Mexico. A special methodology based on a decision support system was developed. This methodology allows to decide if it is convenient or not to finance a reclamation or reuse project for the most common water uses in the basin. This methodology is based on the net present value criteria (NPV) of the effective cash flow during the useful life of the project. The results obtained reveal a technical and economical feasibility for industrial reuse in Jiutepec and for agricultural reuse in Zacatepec and Emiliano Zapata. On the other hand, sanitation projects are not feasible in all cases analyzed. Therefore, Mexican Regulation (Ley Federal de Derechos en Materia de Agua) as currently implemented, does not promote and support this kind of projects.     

Evaluating the economic viability of solar-powered desalination: Saudi Arabia as a case study

Abstract

This article constructs a cost calculator to estimate the economic competitiveness of solar-powered desalination in Saudi Arabia. Solar desalination is defined as a plant that obtains solar energy from a closed system. This is done to focus the investigation on desalination technologies, rather than the efficacy of replacing conventional energy sources with renewables in an integrated electricity grid. The results suggest that current options for solar-powered desalination are not cost-competitive compared to incumbent technologies in Saudi Arabia. The article offers insight into where costs must decrease before solar technologies are economically competitive in the country.     

Chronology of rainbow trout reproduction in a warmwater tributary of the Chattahoochee River: using an invasive species as an indicator of watershed integrity

The Chattahoochee River near Atlanta, Georgia, USA is a stocked tailwater trout (Salmonidae) fishery and rainbow trout (Oncorhynchus mykiss) have been found to spawn in selected warmwater tributary streams. Because these stocked fish enter non‐stocked waters and produce offspring that reside year‐round, they are technically invasive. One tributary in particular, Cabin Creek, has had documented spawning activity for three consecutive years since the stream was monitored. We chronicled the production of the 2006 year‐class of rainbow trout in this small, warmwater tributary to the Chattahoochee River. Based on electrofishing samples and otolith microstructure, the 2006 year‐class of trout were produced from spawning that occurred from 6 February 2006 to 10 March 2006. Fish from this year‐class grew from an average size of 34.28 mm total length (TL) on 26 April 2007 to 102.00 mm TL on 14 May 2007, which is an average increase in size of 67.72 mm over a 383‐day period or 0.18 mm/day. Water temperatures in the stream were near the lethal limits for rainbow trout, reaching a maximum of 24.57°C on 1 August 2006 and a maximum 7‐day average maximum (M7DAM) of 22.99°C on 7 August 2006. The watershed of Cabin Creek is one of the least urbanized in the area, protected from development within lands owned by the National Park Service, with high levels of forest cover, which facilitates rainbow trout young‐of‐year survival through the summer. Thus, the documented spawning and young‐of‐year survival of this invasive species appears to be indicative of high forested watershed integrity. Copyright © 2008 John Wiley & Sons, Ltd.