Disappearance Of Lakes Research Articles

Soil Cover Modifications in Vicinity of Disappearing Lakes as a Result of Climate Change

Abstract Disappearance of lakes is one of the most dangerous processes affecting the entire natural environment, including soil. This phenomenon is considered natural, resulting from climate change, however in recent decades, a significant acceleration of this process has been observed due to the direct impact of human activity. In areas directly adjacent to lakes, organic soils usually predominate. Unfortunately, wetlands are increasingly being drained and used for agricultural purposes. Under such circumstances, changes in the physical and chemical properties of these soils are often irreversible, causing their degradation. As an effect of increased mineralization, a number of typical modifications occur in soils, such as carbon loss, increased degree of peat decomposition, and changes in soil structure. Long-term dehydration has led to muck formation. Additionally, lowering of lake water uncovers previously flooded areas and increases the intensity of soil-forming processes. However, the presence of the Subaquatic qualifier in the World Reference Base for Soil Resources (WRB) suggests that sediments in shallow water bodies no more than 200 cm deep can also be classified as soils. The progressive disappearance of lakes observed all over the world is therefore a process affecting not only the reduction of water bodies, but also changes in the properties and typology of soils and vegetation cover.

Limited extension of the MIS 2 proglacial lake in the Severnaya Dvina valley, south‐eastern margin of the last Scandinavian Ice Sheet

ABSTRACTThe Severnaya Dvina River valley crosses the former south‐eastern margin of the last Scandinavian Ice Sheet. Despite a long research history, there remains considerable controversy about the maximum ice‐sheet extent and the expansion of proglacial lakes within the Severnaya Dvina fluvial system. The goal of this study was to address these issues using new material from the valleys of the Severnaya Dvina and the lower Vychegda, thereby contributing to an understanding of the history of the south‐eastern sector of the last Scandinavian Ice Sheet and its periglacial areas. We studied a number of geological sections using radiocarbon and optically stimulated luminescence (OSL) dating, pollen and carpological analyses, and found that the Last Glacial Maximum (LGM) proglacial lake occupied the Severnaya Dvina valley between 20–19 ka and about 15.5 ka. The lake was localized within the proglacial isostatic depression and occupied only the Severnaya Dvina valley extending no further than the confluence of the Vychegda River, no more than 110 km from the edge of the ice sheet. The lake formation did not cause any drainage reorganization within and outside the Vychegda fluvial system. Given the small size of the lake and presence of the oldest OSL ages along the entire length of the former lake, we suggest that the onset of the proglacial lake marks the maximum extent of the ice sheet in the area. Consequently, the onset of the local LGM may be dated to 20–19 ka, somewhat earlier than assumed by most previous researchers. The LGM ice sheet boundary was located in the Severnaya Dvina valley downstream from the Vychegda confluence and did not extend into the Vychegda valley, despite previous suggestions. During deglaciation, the lake disappearance together with crustal rebound caused an incision episode in the Vychegda – Severnaya Dvina system and the formation of the Lateglacial alluvial terrace with relative height rising downstream due to the uneven rates of the postglacial uplift.

Paleo-lake evolution influenced by tectonic processes and climate changes in the Hetao Basin during the late Quaternary

Exploration of paleo-lake evolution is crucial for the understanding of climatic and tectonic roles in earth surface. Previous studies mainly focused on the climatic effect on river-lake transitions and lake evolutions through lacustrine deposits, but with limited consideration of tectonic drivers, especially for the tectonic rift lakes in the Hetao area.Based on the analyses of lacustrine and fluvial piedmont terraces and a 400-m core from the northern Hetao Basin, along with the optically stimulated luminescence and detrital zircon U-Pb dating, we adopted an integrated “tectonics-climate-surface processes” approach to explore the climatic and tectonic effects on the lake evolution of the Hetao rift basin. Results show that lacustrine deposition on the piedmont terrace T1 (60–47 ka), underlying the T3 fluvial (80–60 ka), has an erosion contact with pluvial deposits at 55 ka, implying the paleo-lake formation at ∼ 80–60 ka and shrinkage at ∼ 55–47 ka. Lake formation was forced by basin depression under the tensile stress of tectonic movement, and was recharged by the Yellow River due to obstruction of the outlet at Tuoketuo caused by uplift.Lake shrinkage was due to the combined effect of basin lifting and warm-wet climate conditions that promoted outflow. A substantial decrease in the erosion base level and rapid water drainage induced by river cutting caused erosion of lacustrine deposits in the basin. The limited sedimentary space of the lake basin in early MIS 2 should be considered a factor in lake disappearance in addition to the dry climate. This study highlights that tectonic effects may be more important than climatic effects in the evolution of rift lakes near the young fold mountain belts.

Analysis of tsagaan lake sediment, valley of the gobi lakes, Mongolia, to determine past environmental changes and the effect of ongoing global warming

The arid region of Mongolia is sensitive to climate change. Understanding of climate variations in the past plays an important role in predicting further climate changes. In this study, we aim to investigate the relationship between the climatic factor and sedimentation history in the late Holocene. We analyzed the 18TS1 core sample (136 cm in length) from the Tsagaan lake in the Valley of the Gobi Lakes, Mongolia. The sediment core mainly consists of clay and silt sediments, occasionally interrupted by the sand-dominated layers. 210Pb dating method is applied and indicates that the upper 24 cm sediment spans the sedimentation history of the last 87 years. Along-core variations in sediment characteristics such as organic matter, carbonate, and amorphous silica abundance are indicative of the drought -inducing period based on the significant correlations between sediment characteristics and Self-calibrated Palmer Drought Severity Index. Moreover, the enrichment of carbonates is a great indicator of shallow lake conditions prior to the lake disappearance during the dry period. The chemical composition of sand-dominated units in the sediment core well agrees with that of sand sheets and sand dunes in the catchment. Modern expansion and migration of sand sheets are identified by aerial photo imagery. The insufficient sediment chronology is limiting our interpretation, though; the comparison with the other paleoclimate records helps the establishment of environmental changes in the last millennium.

Lake aging concept revisited: alternative comprehensive approach to lake ontogeny

The only available theoretical model explaining the natural development of lakes is a set of assumptions underlying the so-called lake aging concept (LAC). It incorrectly states that with time, lakes age and are inevitably and unidirectionally subject to eutrophication processes. In its most radical version, it misidentifies eutrophication, i.e., an increase in productivity resulting from enrichment in nutrients, with progressive disappearance of lakes over geological timescales due to the filling of the basin with sediment. To this day, LAC assumptions are referred to in various sources, including scientific articles, the Internet, official government documents, as well as teaching materials, all despite a critical approach to this concept presented in several publications, including limnology textbooks. This article, for the first time, presents the history of creation of LAC and an analysis of its main assumptions. A new alternative approach to explain lake ontogeny is also proposed, based on the current knowledge from several environmental sciences, including limnology, physical geography, and paleoecology.

Geophysical–geotechnical methodology for assessing the spatial distribution of glacio‐lacustrine sediments: The case history of Lake Seracchi

AbstractProglacial lakes are distinctive features of deglaciated landscapes and often act as sediment sinks, collecting solid material from subglacial erosion or washout of deglaciated areas. The solid transport flow, strongly linked to the glaciers and periglacial landforms, may rise due to the rapid changes driven by climate warming, causing deep transformations in the basin hydrology, and even the appearance or disappearance of lakes at a decadal timescale.The goal of this study was to present a geophysical–geotechnical approach that integrates several techniques, to quantify the sediment distribution in a proglacial lake. A geophysical survey is performed with ground‐penetrating radar (GPR) installed on a boat, whereas a time‐domain reflectometer (TDR) measures the electrical conductivity and permittivity of the lakebed sediments. Unperturbed samples are collected and analyzed to measure the main geotechnical properties of the sediment: grain‐size distribution, plastic limit, and liquid limit. Such properties support the interpretation of the GPR data and the detection of spatial variations of the sediment facies.To validate the proposed methodology, field tests were carried out at Lake Seracchi, the largest lake of the Rutor glacier, Italian Alps. It formed around 1880 because of the recent glacier shrinkage, as chronicled by valuable historical documents. Its greyish waters carry a significant amount of suspended sediment recognized as glacial flour, which gradually accumulates on the bottom of the lake.The obtained bathymetry and sediment thickness maps of Lake Seracchi show the strength of the approach: from only a few manual samples, it is possible to extrapolate the geotechnical properties of interest, such as friction angle or hydraulic conductivity, to wider areas, surveyed by the geophysical techniques. This is achieved by investigating the spatial distribution of key geophysical properties linked to the geotechnical properties of interest.

Zmiany powierzchni wybranych jezior Pojezierza Łęczyńsko-Włodawskiego

An attempt was made to evaluate the process of lake disappearance over the years 1886-2019 in the Łęczna-Włodawa Lake District. The analysis were based on archival cartographic materials (WIG maps published in 1936 and maps in the PUWG 1965 system) and on vector map based on BDOT10k. It was determined that over a period of 133 years, the surface area of selected natural water reservoirs was reduced by 10,26%. Changes have been influenced by many factors: the building of the Wieprz-Krzna canal and the drainage system connected with it, agricultural land use, rapid development of tourism and coal mining. Results presented in this paper show that the greatest risk of decreasing of lake area concerns reservoirs of small size (<50 ha) due to their more limited ability to self-purificate and lower resistance to degradation. A greater change was observed in the case of lakes located in the Poleski National Park and its buffer zone (-16,51%) than in the case of other studied water reservoirs (-8,91%).

LANDSCAPE-ECOLOGICAL BASES OF HUMANIZATION OF ARCHITECTURAL AND TOWN-PLANNING INFRASTRUCTURE OF URBAN ENVIRONMENT

Formulation of the problem. The territory of any city is characterized by two main indicators: the natural basis created in the process of urban planning, planning and construction. The combination of these factors shapes the urban environment. At all stages of development of civilization sought to create a comfortable urban environment for the livelihood of the population primarily taking into account human needs. Purpose of the article is to investigate in the process of urbanization the relief of the assimilated territory is processed in accordance with the needs of a particular stage of city development. Comparison of several sections of the relief of the same urban area allows to establish changes in the composition of the earth's surface that have already occurred: the disappearance of lakes, river flows, ravines, straightening the riverbed, the emergence of a new reservoir, changes in altitudes. An urgent complex urban planning problem today is to determine the prospects for further development and reconstruction of large industrial cities. Ergonomic factor allows, above all, to create a comfortable environment for production activities, as well as a recreational environment in which a person in the process of rest could feel comfortable psychologically and emotionally. Humanization − the humanization of the production environment − is based on ergonomics, taking into account, above all, new technologies and the impact on the city's ecosystem. Conclusions. The dynamic transformation of the city under the influence of various factors was accompanied by a change of approaches to correct the contradictions that arise from the interaction of natural and artificial components of the urban environment with architectural and urban infrastructure. The living environment at each stage of historical development has changed, primarily taking into account its architectural and urban infrastructure, and each stage of historical development has changed the nature of the relationship “city − environment – man”.

Foam-based floatovoltaics: A potential solution to disappearing terminal natural lakes

Terminal lakes are disappearing worldwide because of direct and indirect human activities. Floating photovoltaics (FPV) are a synergistic system with increased energy output because of water cooling, while the FPV reduces water evaporation. This study explores how low-cost foam-based floatovoltaic systems can mitigate the disappearance of natural lakes. A case study is performed on 10%–50% FPV coverage of terminal and disappearing Walker Lake. Water conservation is investigated with a modified Penman-Monteith evapotranspiration method and energy generation is calculated with an operating temperature model experimentally determined from foam-based FPV. Results show FPV saves 52,000,000 m3/year of water and US$6,000,000 at 50% FPV coverage. The FPV generates 20 TWh/year of renewable energy, which is enough to offset all coal-fired power plants in Nevada thus reducing carbon-emission based climate forcing partially responsible for a greater rate of disappearance of the lake. The results of this study, which is the first of its kind, indicate foam-based FPV has potential to play a crucial role in mitigation efforts to prevent the disappearing of natural lakes worldwide.

Runoff controls the development of eco-hydrological and economic conditions in an arid oasis of the downstream inland river basin

Oasis degradation and terminal lake shrinkage are prevalent consequences of the disputed distribution of water resources in inland river basins, hindering regional sustainable development. The Ecological Water Diversion Project (EWDP) is regarded as an important measure to restore the desert-oasis ecosystem in inland river basins, and thus it is essential to comprehensively evaluate the response of eco-hydrological and socioeconomic systems to the EWDP. Based on multiple indicators, we used trend analysis, linear regression, partial least square regression, and structural equation model to disentangle the quantitative effects of the EWDP on the change of eco-hydrological and socioeconomic conditions in the Ejina Oasis (EO) in the lower reaches of the Heihe River in northwest China. Our results indicate that the ecological deterioration was prevalent before the execution of the EWDP, including the increase of groundwater depth, the disappearance of lakes, the decrease of NDVI. After the EWDP, runoff released to EO increased 69.15%, the mean groundwater depth decreased 0.48 m, 52.28% of the study area showed a significant increase in NDVI, areas of forest and grassland increased 20.17 and 25.65 km2, respectively. The EWDP improved the hydrological regime and prompted the recovery of the oasis. Besides, socioeconomic development was facilitated under the restoration of the eco-hydrological conditions, characterized by the expansion of farmland and the thrive of the tourism industry. The hydrological variables promoted the improvement of the ecological condition with a direct strength of 0.93 and facilitated the development of the socioeconomic conditions in EO with an indirect strength of 0.84. Runoff was the most important positive contributor both to the NDVI and GDP in EO. This comprehensive evaluation framework can offer valuable insight for water resources management and sustainable development in the inland river basin of arid areas.

Stages of soil development in the coastal zone of a disappearing lake\u2014a case study from central Poland

PurposeThe aim of this study was to estimate the impact of lake disappearance, groundwater table fluctuations, and some aspects of human pressure on stages of soil cover development in the catchment of Lake Rakutowskie.Materials and methodsResearch was conducted in soil chronosequence composed of eight soil profiles located in 785-m-long transect. Soils were sampled every 10 cm. Physical and chemical properties were determined with the use of disturbed and undisturbed samples. Radiocarbon dates were obtained for the bottom part of peat in each soil profile. The mineral composition of selected soil samples was determined using the X-ray diffraction (XRD) method. Additionally, the hydrological conditions were continuously monitored from July 27, 2013 to September 23, 2014.Results and discussionAn increased rate of shallow lakes overgrowth and final disappearance is a commonly observed process in the European lowlands. This paper presents and discusses the influence of changes in the range of the Lake Rakutowskie wetlands complex (central Poland) and water level fluctuations on soil cover transformation in the immediate vicinity of the lake. Five major phases of soil cover development (from Subaquatic Histosols (Limnic) to Hypereutric Regosol (Drainic, Humic)) were hypothetically reconstructed based on detailed studies of soil physical and chemical properties, mineral composition, water level fluctuations, and radiocarbon dating. The degree of peat decomposition in the studied profiles increased with the distance from the contemporary lake surface. Along with the progressive dehydration and mineralization of organic soils, their physical and chemical properties deteriorated, which is visible, e.g., in soil structure, and mineral and chemical composition (especially TOC and TN). Obtained radiocarbon ages of selected samples indicate that the oldest peat layers developed about 5856 cal BCE (6970 ± 70 14C BP), while the youngest were deposited about 1074 cal CE (980 ± 40 14C BP)–1573 cal CE (300 ± 35 14C BP). Hydrological studies indicate a progressive process of lake disappearance.ConclusionsThe process of soil cover transforming of the studied area takes place relatively quick, mainly recently due to the influence of human activity. Based on these results, it can be predicted that the lake will most likely disappear in a relatively short time, and the soil cover will be entirely in the fifth phase (P5) of evolution.

Relationships between Temporal and Spatial Changes in Lakes and Climate Change in the Saline-Alkali Concentrated Distribution Area in the Southwest of Songnen Plain, Northeast China, from 1985 to 2015

The southwest of Songnen Plain, Northeast China, has an arid climate and is a typical concentrated distribution area of saline-alkali soil. The terrain here is low-lying, with many small, shallow lakes that are vulnerable to climate change. This paper used Landsat satellite remote sensing images of this area from 1985 to 2015 to perform interpretation of lake water bodies, to classify the lakes according to their areas, and to analyze the spatial dynamic characteristics of lakes in different areas. During the 30 years from 1985 to 2015, the number of lakes in the study area decreased by 71, and the total lake area decreased by 266.85 km2. The decrease was more serious in the east and northeast, and the appearance and disappearance of lakes was drastic. The Mann–Kendall test method was used to analyze trends in meteorological factors (annual mean temperature, annual precipitation, and annual evaporation) in the study area and perform mutation tests. Through correlation analysis and multiple generalized linear model analysis, the response relationship between lake change and climate change was quantified. The results showed that the average temperature in the area is rising, and the annual precipitation and evaporation are declining. Temperature and precipitation mainly affected lakes of less than 1 km2, with a contribution rate of 31.2% and 39.4%, and evaporation had a certain correlation to the total lake area in the study area, with a contribution rate of 60.2%. Small lakes are susceptible to climatic factors, while large lakes, which are mostly used as water sources, may be influenced more by human factors. This is the problem and challenge to be uncovered in this article. This research will help to improve our understanding of lake evolution and climate change response in saline-alkali areas and provide scientific basis for research into lakes’ (reservoirs’) sustainable development and protection.

Impact of Lake Morphology and Shallowing on the Rate of Overgrowth in Hard-Water Eutrophic Lakes

Lake disappearance is one of the results of water eutrophication which leads to lake shallowing and overgrowth, and small and shallow lakes are the most threatened with degradation. We studied the effect of lake shallowing on its overgrowth, taking into account the morphometric parameters of water bodies. The study was performed in 20 lakes located in the central west part of Poland. The degree of lake shallowing was evaluated on the basis of bathymetric maps made in the 1960s and studies carried out presently. Additionally, an analysis of littoral coverage and macrophyte growth forms was investigated. Moreover, the composition, intensity of phytoplankton blooming, and physico-chemical parameters of the lake water were analyzed. Redundancy analysis shows that the lake volume, average depth, shallowing rate, and change in volume were the parameters that most strongly correlated with the share of macrophytes in the lakes. According to the regression analysis, the share of emergent macrophytes was significantly correlated with lake shallowing. No relation was found between phytoplankton abundance and lake shallowing. Conversely, the lakes with the highest rate of shallowing were characterized by the greatest share of vegetation, which suggested that vegetation growth had a significant impact on lake shallowing.

Drainage integration and sediment dispersal in active continental rifts: A numerical modelling study of the central Italian Apennines

AbstractProgressive integration of drainage networks during active crustal extension is observed in continental areas around the globe. This phenomenon is often explained in terms of headward erosion, controlled by the distance to an external base‐level (e.g. the coast). However, conclusive field evidence for the mechanism(s) driving integration is commonly absent as drainage integration events are generally followed by strong erosion. Based on a numerical modelling study of the actively extending central Italian Apennines, we show that overspill mechanisms (basin overfilling and lake overspill) are more likely mechanisms for driving drainage integration in extensional settings and that the balance between sediment supply vs. accommodation creation in fault‐bounded basins is of key importance. In this area drainage integration is evidenced by lake disappearance since the early Pleistocene and the transition from internal (endorheic) to external drainage, i.e. connected to the coast. Using field observations from the central Apennines, we constrain normal faulting and regional surface uplift within the surface process model CASCADE (Braun & Sambridge, 1997, Basin Research, 9, 27) and demonstrate the phenomenon of drainage integration, showing how it leads to the gradual disappearance of lakes and the transition to an interconnected fluvial transport system over time. Our model results show that, in the central Apennines, the relief generated through both regional uplift and fault‐block uplift produces sufficient sediment to fill the extensional basins, enabling overspill and individual basins to eventually become fluvially connected. We discuss field observations that support our findings and throw new light upon previously published interpretations of landscape evolution in this area. We also evaluate the implications of drainage integration for topographic development, regional sediment dispersal and offshore sediment supply. Finally, we discuss the applicability of our results to other continental rifts (including those where regional uplift is absent) and the importance of drainage integration for transient landscape evolution.

Indicator Values of Emergent Vegetation in Overgrowing Lakes in Relation to Water and Sediment Chemistry

Lake overgrowth is one of the mechanisms affecting the gradual disappearance of lakes in the temperate zone caused by excessive eutrophication of waters. The aim of this study was to assess the possibility of using helophytes as bioindicators of lake overgrowth based on long-term changes based on the cartographic maps studies (1911–2012) and field analyses of plant form growth cover (2012–2014). Additionally, water and sediment chemistry in overgrowing lakes were investigated. The study comprised a total of 33 eutrophic lakes characterized by varying degrees of vegetation development. Based on discriminant analysis, four groups of lakes with diverse degrees of vegetation growth were distinguished. The group comprising the most overgrown water bodies was found to have the greatest percentage of helophytes, with a considerable proportion of submerged and floating-leaved macrophytes. Based on a review of archival materials, lakes which currently exhibit the highest degree of overgrowth were shown to have been affected by intensive littoral growth for over 100 years, which confirms bioindicator properties of helophytes in the assessment of the degree of lake overgrowth. In addition, lakes with the highest rate of overgrowth were characterized by a high content of nitrogen in sediment, with a concurrent high concentration of potassium.

Analysis and Visualisation of Lake Disappearance Process in Iława Lakeland Landscape Park

Abstract Lake disappearance as a natural stage of evolution of lakes is an extremely important issue in the landscape and ecosystem research context. Studies of the changes that occur in the lake landscape, characteristic in the northern part of Poland, are aimed at defining the cause and forecasting the results. The possibilities of the Geographic Information Systems (GIS) were used in this paper to analyse and visualise the process of lake disappearance in the Iława Lakeland Landscape Park. GIS technologies which primarily are used for gathering, storing, processing and presenting spatial data have been used to interpret changes in lakes coverage over a period of 100 years. The analysis were based on data bases and cartographic former maps such as hydrographic maps, attribute data and bathymetric plans. The data was gathered by transfer from different geoportals, next vectorised, and then preprocessed. Former maps were rectified. The lake disappearance process was presented in several forms: lake cards, animations and interactive map. Basing on the GIS analysis about lake disappearance in Iława Lakeland Landscape Park it was possible to state that lakes are disappearing in rate of 3.99 ha a−1.

Assessment of selected physicochemical properties of restorated water of the Mogileriskie Lake

Excessive supply of nutrients contributes to gradual eutrophication of water. This process can happen fast, especially in shallow lakes which are more prone to degradation. This also causes deterioration of settlement conditions of many organisms and limits economic use of water. Eutrophication can lead to gradual shallowing and shrinking of water reservoirs and subsequently disappearance of lakes. Therefore, appropriate diagnosis and reduction of the amount of pollutantsflowing into lakes are crucial for the water quality improvement and prevention from further degradation. The Mogileńskie Lake, like many other town lakes was supplied with sewage. As a consequence, the reservoir stopped being an attractive urban element, and became an object cumbersomeaud dangerous to the residents health. For this reason the lake has been subjected to many protection and reclamation processes.The water samples were taken 10 times from 3 sampling points between September 2014 and June 2015. The contents of total phosphorus, phosphorates, total nitrogen, nitrates, nitrites, and ammonium nitrogen was measured in the tested water. The results obtained from the water analyzed for biogenic elements, and their compounds indicate low effectiveness of the carried out reclamation. According to many authors, the choice of artificial aeration as a reclamation process for the Mogileńskie Lake was a mistake.This cleaning method does not provide the expected results when used for shallow and polymictic lakes, especially in combination with an invasive method of dredging and the controversial deposing of the extracted residues in the direct proximity of the lake.

A regional-scale assessment of Himalayan glacial lake changes using satellite observations from 1990 to 2015

The Himalaya, the world's highest mountain ranges, are home to a large group of glaciers and glacial lakes. Glacial lake outburst floods (GLOFs) in this region have resulted in catastrophic damages and fatalities in the past decades. The recent warming has caused dramatic glacial lake changes and increased potential GLOF risk in the Himalaya. However, our knowledge on the current state and change of glacial lakes in the entire Himalaya is limited. This study maps the current (2015) distribution of glacial lakes across the entire Himalaya and monitors the spatially-explicit evolution of glacial lakes over five time periods from 1990 to 2015 using a total of 348 Landsat images at 30m resolution. The results show that 4950 glacial lakes in 2015 cover a total area of 455.3±72.7km2, mainly located between 4000m and 5700m above sea level. Himalayan glacial lakes expanded by approximately 14.1% from 1990 to 2015. The changing patterns of supraglacial lakes and proglacial lakes are rather complex, involving both lake disappearance and emergence. Many emergent glacial lakes are found at higher elevations, especially the new proglacial lakes, which have formed as a result of glacier retreat. Spatially heterogeneous changes of Himalayan glacial lakes are observed, with the most significant expansion occurring in the southern slopes of the central Himalaya. Increasing glacier meltwater induced by the Himalayan atmospheric warming is a primary cause for the observed lake expansion. This study provides primary data for future GLOF risk assessments. A total of 118 rapidly expanded glacial lakes are identified as potential vulnerable lakes for the priority of risk assessment.

Ecology-oriented groundwater resource assessment in the Tuwei River watershed, Shaanxi Province, China

In arid and semi-arid regions, a close relationship exists between groundwater and supergene eco-environmental issues such as swampiness, soil salinization, desertification, vegetation degradation, reduction of stream base flow, and disappearance of lakes and wetlands. When the maximum allowable withdrawal of groundwater (AWG) is assessed, an ecology-oriented regional groundwater resource assessment (RGRA) method should be used. In this study, a hierarchical assessment index system of the supergene eco-environment was established based on field survey data and analysis of the supergene eco-environment factors influenced by groundwater in the Tuwei River watershed, Shaanxi Province, China. The assessment system comprised 11 indices, including geomorphological type, lithology and structure of the vadose zone, depth of the water table (DWT), total dissolved solids content of groundwater, etc. Weights for all indices were calculated using an analytical hierarchy process. Then, the current eco-environmental conditions were assessed using fuzzy comprehensive evaluation (FCE). Under the imposed constraints, and using both the assessment results on the current eco-environment situation and the ecological constraint of DWT (1.5–5.0 m), the maximum AWG (0.408 × 108 m3/a or 24.29 % of the river base flow) was determined. This was achieved by combining the groundwater resource assessment with the supergene eco-environmental assessment based on FCE. If the maximum AWG is exceeded in a watershed, the eco-environment will gradually deteriorate and produce negative environmental effects. The ecology-oriented maximum AWG can be determined by the ecology-oriented RGRA method, and thus sustainable groundwater use in similar watersheds in other arid and semi-arid regions can be achieved.

Conflitos pela água em tempos de seca no Baixo Jaguaribe, Estado do Ceará

Este trabalho analisa os impactos ambientais e socioeconômicos da seca de 2012 a 2014 na microrregião do Baixo Jaguaribe do estado do Ceará, com o objetivo de compreender como a população reage à crise ambiental, seja pela aprendizagem e auto-organização a partir da experiência de escassez, seja pelo aumento dos conflitos por acesso à água. Verifica-se que houve o desaparecimento de lagoas e açudes equivalente a uma área de 300 km2, entre 2009 e 2014, em dois municípios da região. Ademais, pode-se destacar o surgimento de conflitos socioambientais em razão da escassez de água, mesmo em um dos territórios mais privilegiados do Semiárido com a presença de rios, lagoas e açudes. Há conflitos associados ao acesso e distribuição da água entre as empresas dos perímetros irrigados, os pequenos agricultores, a Região Metropolitana de Fortaleza, a população de municípios da região e o Movimento dos Trabalhadores Rurais sem Terra (MST).