Lake Desiccation Research Articles

Iran as Subaltern Empire: Lake Orumiyeh, Environmental Injustice, and Coloniality in Iranian Azerbaijan

AbstractIn recent years, protests have emerged to save Lake Orumiyeh, which has nearly vanished following decades of agricultural development, dam building, and drought. Lake Orumiyeh is located in Iranian Azerbaijan, which sits at the intersection of three former empires: Persian, Ottoman, and Russian. Iranian Azerbaijan is largely comprised of ethno‐linguistic minority communities that are unevenly impacted by environmental hazards stemming from the lake's desiccation, and protests to save the lake are generally characterised as environmental conflict resulting from climate change or as a reflection of ethno‐nationalist tensions in Iran. These readings, however, fail to account for how imperial pasts and colonial presents shape exposure to environmental violence. This article posits that environmental violence functions as a form of coloniality and, using Lake Orumiyeh as an entry point, aims to: (i) examine coloniality in a country that was never formally colonised yet impacted by different formations of empire; (ii) account for subjectivities shaped through non‐Western European forms of imperialism; and (iii) connect racialised difference in Iran to the reproduction of colonial and racial logics vis‐à‐vis European imperialism.

Dust over water: Analyzing the impact of lake desiccation on dust storms on the Iranian Plateau

The desiccation of lakes on the Iranian Plateau, driven by both natural processes and anthropogenic activities, has led to significant land cover changes, exposing lake beds and triggering adverse environmental consequences. These transformations pose serious threats to ecological conditions and the provision of ecosystem services. This study investigates the potential links between lake desiccation and the occurrence of dust storms across major lakes on the Iranian Plateau. By utilizing remote sensing data and time series statistical analysis, including the Mann-Kendall test, Ordinary Least Square (OLS) regression, and frequency analysis, we assessed changes in lake extent and their effects on Aerosol Optical Depth (AOD) and Particular Matter (PM2.5) from 1985 to 2020. An analysis of Landsat imagery reveals that lake desiccation commenced in the late 1990s, exhibiting a marked downward trend that has intensified in recent years. The results show a significant inverse correlation between aerosol parameters (AOD and PM2.5) and lake extent. Reduced lake area is associated with elevated AOD and PM2.5 concentrations, with the highest aerosol levels observed when lakes reach their smallest extent. Notably, despite an 81 % reduction in the lake area, dust storm occurrences have increased by 20%. These findings highlight the critical role of lake desiccation in exacerbating dust storms in the surrounding regions. Furthermore, the temporal alignment between fluctuations in lake extent and dust storm frequency is validated through regression analysis with a 95 % confidence level. The consistency between our results and existing literature underscores the reliability of the observed relationship, emphasizing the urgent need to address the environmental consequences of lake desiccation to mitigate its broader ecological impacts and potential human health impacts.Graphical Abstract

Assessing the oxidative potential of dust from great salt Lake

Great Salt Lake (GSL) is one of the world's largest inland bodies of saltwater. Climate change, drought, and water diversions have led to the GSL reaching historically low levels, exposing over 1945 km2 of lakebed. Dust events can transport particulate matter (PM) from the GSL's exposed lakebed to the adjacent urban areas, presenting air quality and health concerns. In this study, we assessed the oxidative potential (OP) of dust from the exposed GSL bed compared to dust samples collected from other regional playas and to reference Arizona test dust. The oxidative potential of PM10 (particles ≤10 μm in aerodynamic diameter) derived from these dusts was assessed by two acellular assays: the ascorbic acid (OPAA) and dithiothreitol (OPDTT) and two extraction solvents: phosphate buffer saline and Gamble's simulated lung fluid. All samples were also analyzed for elemental composition. Our results show that the concentration of As and Li in most of the GSL dust samples exceeded the Environmental Protection Agency (EPA) soil residential regional screening levels, and the OPAA and OPDTT of dust samples from GSL playas were generally higher than the OP of other regional playas. Our findings also indicated that the OP of the GSL dust was associated with metals, including Cu, Mn, Fe, and Al. This is the first study evaluating the oxidative potential of dust from the GSL, which improves our understanding of how increasing aridity, particularly desiccation of saline lakes, affects air quality and public health.

Anthropogenic vs. climatic drivers: Dissecting Lake desiccation on the Iranian plateau

Lakes are indispensable to ecological balance, supporting biodiversity and human welfare. Despite their importance, lakes around the globe are diminishing at an alarming rate, presenting substantial environmental challenges exacerbated by climate variability and human-induced pressures, such as unsustainable land management and excessive water withdrawals. This study offers an extensive analysis of the desiccation phenomena affecting major lakes on the Iranian plateau, dissecting the complex interplay of contributing factors. We examine meteorological, hydrological, and agricultural drought conditions using indices like SPI, SDI, and SPEI to gain nuanced insights into drought dynamics. This study sheds light on the factors that contribute to the drying up of lakes and quantifies the impact of anthropogenic and climatic drivers on this phenomenon. The findings indicate that the area of all lakes has declined dramatically after the change point, ranging from 51% in the Urmia Lake to an impressive rate (i.e. 100%) in Southern Hamun. Despite the stable rate of meteorological droughts (increasing in temperature by about 1 °C since the 90s and stable precipitation patterns across most basins), the research highlights the ongoing struggle against severe hydrological and agricultural drought conditions. The study delineates the predominant role of anthropogenic activities in the diminishing lake inflows and the consequential drying of the lake, accounting for approximately 100 % in five of the seven lakes.

The influence of Urmia Lake desiccation on an extreme snowfall event: A case study using the WRF-Lake model

Urmia Lake in the northwest Iran has undergone significant desiccation in recent decades, shrinking to a much smaller size than its original. This study implements the WRF-Lake coupled modeling system to examine the impacts of the observed physical changes over the Lake during a heavy snowfall event occurred February 1–2, 2017. Modifications are introduced to represent the shrunken, salt-encrusted lake surface and surrounding arid environment through updating land use, soil characteristics, lake size and depth, and albedo data. Experiments incorporating lake-atmosphere coupling and land surface refinements (Lake_CTL, Lake_LULC, Lake_AL) outperform simulations without a lake (WRF_noLake) in reproducing observed precipitation patterns at stations surrounding the Urmia Lake. All simulations underestimate the extreme 290 mm snowfall recorded at the Urmia station; however, the Lake_LULC and Lake_AL improve snowfall representation at other stations around the lake. Regarding snow cover validation, Lake_LULC and Lake_AL exhibit a higher correlation with satellite observations and show a significant improvement in snow detection near Urmia Lake. They have a Probability of Detection (POD) of 0.94 and a Critical Success Index (CSI) of 0.91, compared to a POD of 0.79–0.80 and a CSIs of ∼0.77 for the default lake model (Lake_CTL) and the WRF_noLake experiments, respectively. Additionally, adjusting the initial lake surface temperature to match observations substantially reduces cold biases in near-surface air temperatures over Urmia Lake. The lack of lake temperature updating in WRF-Lake poses ongoing challenges in the model, though. In summary, this study demonstrates that refining the representations of desiccated lakes and their surroundings in high-resolution coupled models would improve simulations of meteorological processes influenced by lake-atmosphere interactions.

A comprehensive investigation of the causes of drying and increasing saline dust in the Urmia Lake, northwest Iran, via ground and satellite observations, synoptic analysis and machine learning models

Nowadays, dried lakes have turned into important dust sources with serious environmental, climatic and socio-economic impacts. In this study, climatic, terrestrial and anthropogenic effects that caused desiccation of the Urmia Lake, NW Iran are investigated. The main objective is to assess the influence of climatic and regional factors against anthropogenic and local ones in the dryness of the lake during the last two decades. Annual temperature, precipitation and wind speed data measured at nearby meteorological stations, along with water discharge of eight main rivers flowing into the lake are analyzed. The results reveal that the main cause for turning Urmia into a dried lake bed was human interference, since climatic factors contributed positively but to a lesser degree, while terrestrial factors may also play a crucial role. Among anthropogenic interferences, the construction of a causeway had a weak effect in the lake's dryness, while construction of many river dams highly contributed to this disaster. Furthermore, four machine learning models showed that groundwater decline is also an important factor for lake's desiccation. Analysis of dusty days at stations in the Urmia Basin showed similar inter-annual and seasonal dust variability over the whole western Iran. This indicates that dust over the Urmia Basin is mainly affected by the regional dust activity, while the dried lake beds contribute to a lesser degree to the enhanced dust loading. The dominant wind flow is mostly southwesterly, carrying Urmia saline dust toward NE directions, affecting Tabriz city. Three main synoptic clusters, with dipole features consisted of high-pressure systems over Europe, Central Mediterranean and North Africa and low pressure over SW Asia, facilitated strong westerly winds from arid, desert areas of the Middle East toward the Urmia Basin during 118 dust storms in the region.

Response of diatom communities to climate and human disturbance: A 4200-year record from Costa Rica

This study integrates diatom analysis with existing records of pollen, charcoal, elemental composition, and stable light isotopes to expand upon the 4200-year history of human activity and climate change from Laguna Los Mangos in southern Pacific Costa Rica. We counted diatoms in peroxide-treated samples and analyzed community composition using cluster analysis, revealing four distinct assemblage zones with diatom variability most closely correlated with phosphorus, titanium, and organic content. The earliest assemblage (Zone D, 4150–3430 cal yr BP) was dominated by Encyonema silesiacum and Nitzschia incognita and aligned with a period of deforestation, erosion, and abundant macrophytes. Gomphonema affine proliferated in Zone C (3430–2450 cal yr BP), reflecting increased pH and productivity likely caused by agriculture-induced nutrient loading. We attributed the preservation gap from 3290 to 2970 cal yr BP in Zone C to silica depletion and erosional deposition that induced decline in diatom abundance by diluting valve concentrations in lake sediments. Nitzschia incognita and G. affine became the dominant taxa in Zone B (2450–1400 cal yr BP), likely reflecting eutrophy, increasing conductivity, and drying climate. Dominance of Diadesmis confervacea indicated reduced lake level in Zone A (1400 cal yr BP–modern) at the onset of the Terminal Classic Drought (TCD). A hiatus in the record indicates lake desiccation from 950 to 450 cal yr BP. During the Little Ice Age (LIA), diatoms reflect conditions similar to Zone B indicating increased lake level, circumneutral pH, and eutrophy. Refilling of the lake indicates increased precipitation during the LIA despite evidence of severe regional drought reported at other sites. Variable precipitation during this period likely resulted from the combined effects of Spanish contact, agricultural collapse, forest recovery, and shifts in Atlantic and Pacific climate forcing mechanisms. Overall, the Los Mangos diatom record reflects shallow, slightly alkaline, eutrophic conditions influenced by nutrient enrichment, erosion, and deforestation associated with maize agriculture.

Uncovering the effects of Urmia Lake desiccation on soil chemical ripening using advanced mapping techniques

Urmia Lake in Iran has been gradually drying up since the 2000 s, revealing soil that was once underwater. There is limited research on how this drying process affects the distribution of soil chemical ripening in the lakebed sediments. To investigate this, 131 surface soil samples were collected in July 2017 from six zones based on their distance from the lake's shoreline. Elemental concentrations in the samples were measured using a portable X-ray fluorescence (XRF) spectrometer. Five geochemical indices (GCIs) were calculated: Titanium/Zirconium, Barium/Strontium, Silicon/Aluminium, Silicon/R2O3, and the Darmody index. A remote sensing image (Landsat-8 OLI) from the same sampling period was used as environmental covariates to explain the spatial distribution of GCIs. Random forests (RF) and cubist tree models were employed to model and map these GCIs. The bootstrapping method was used to assess the uncertainty of the maps. Results indicated that the RF model performed better than the cubist model based on the concordance values in the validation dataset. Remotely sensed clay minerals ratio and normalized burn ratio were identified as the most significant covariates in making predictions. The study found that the distribution of all geochemical indices was directly related to their distance from the shoreline. Ba/Sr emerged as the best index for detecting soil chemical ripening in the study area. The index displayed the most significant differences between the drying zones. This research demonstrated that combining satellite imagery with GCIs using the digital soil mapping (DSM) technique can effectively detect soil ripening progression.

Brine geochemical changes and salt crust evolution of Lake Urmia in Iran

Gradual desiccation of Lake Urmia (LU) in the northwest of Iran has led to catastrophic water loss by 2022 promoting the salt crust (SC) deposition on the lake bed. Therefore, this study aimed to investigate 1) the effect of water level on the brine composition, 2) the effect of gradual lake desiccation on SC formation, mineralogy and stratification and 3) the SC formation and mineral precipitation in a lab-scale experiment. In 2019, brine and SC samples were collected in July and October, and analyzed for the prevailing ions and minerals. For the simulation experiment, brine samples were added in two vessels and the change in pH, ionic composition and SC evolution were investigated. The wet season brine type changed from Mg-Na-Cl to Na-Mg-Cl and remained unchanged throughout the dry season. In vessels, Mg2+ and Na+ became dominant ions in the surface and subsurface layers respectively, while Cl- remained roughly unchanged; and minerals gradually precipitated from the margins to the center of the vessels based on their solubility. Similar to the lake SCs, in the simulation vessels, halite dominated the SCs and bischofite (MgCl2·6H2O) was detected in most of the vessels’ layers. The formation of oldhamite (CaS) in both in the vessels and the lake SC indicated the prevalence of low oxygen conditions. In the simulation vessel, Calciolangbeinite (K2CaSO4(H2O)4) was one of the first minerals to form along with halite, while Starkeyite (MgSO4·(H2O)4) and Kieserite (MgSO4·(H2O)) were the latest minerals to precipitate. The absence of magnesium sulfate minerals under natural conditions in both newly formed SCs in 2019 and those dated back to 2005, suggested that if the lake level continues to drop, magnesium sulfate minerals will be the final product of the brine. The existence of a dark silicate layer within SC stratification helped to investigate the evaporate deposition at the early stages of SC formation and after the catastrophic shrink. Based in the precipitation of a new layer on top of the submerged SC samples during 2019, a sedimentation rate between 10 and 30 mm/y is calculated with NaCl and CaS as major precipitants.

Onset of dune construction based on archaeological evidence, White Sands, New Mexico

AbstractThe White Sands dune field is the largest gypsum dune system in the world, derived from deflation of paleo-Lake Otero deposits. Understanding the timing of initial dune construction, and therefore lake deflation, is critical for understanding regional landscape evolution, including the history of lake desiccation. The onset of dune construction is currently estimated at ~8000 to 6500 cal yr BP, but numerical age control is limited. Archaeological evidence reported here indicates two older phases of gypsum dune construction. An archaeological site draped over a parabolic dune south of the main dune body contains artifacts dating to >12,200 cal yr BP, providing an upper age limit for the landform. Another site buried within a remnant of the main dune field yielded six statistically identical radiocarbon dates averaging ~8770 cal yr BP. The initial phase of terminal Pleistocene deflation and parabolic dune construction was perhaps localized but correlates with a period of regional aridity. Barchans and crescentic ridges comprising the main dune body developed in the Early Holocene in response to elevated salinity in local ground water and extensive exposures of gypsum available for deflation, likely due to aridity.

Late Quaternary evolution of Daihai Lake in northern China and implications to the variation of the East Asian summer monsoon

Global warming over the past decades has resulted in desiccation of lakes in arid and semi-arid northern China. However, the mechanisms responsible for the sharp fluctuations in water levels for these lakes in this region are still unclear. The water level fluctuations in geological time can provide an analogue to better understand current lake levels’ response to global warming. In this study, a combination of quartz and feldspar luminescence dating techniques was applied to establish the chronologies of two sedimentary sequences related to lake level in the catchment of Daihai Lake, located on the fringe of the East Asian summer monsoon (EASM) domain. Our objective is to reconstruct the late Quaternary history of lake level fluctuations and provide the interpretations of their causes. The results indicate that two lake-level highstands existed during 130–120 ka and 8-4 ka, at least ∼38 m and 40 m above the current lake level, respectively. We interpret that the lake level variations on multiple timescales in the monsoonal marginal area have primarily been regulated by the EASM intensity and corresponding monsoonal precipitation, while temperature changes may have played a minor role. Moreover, a compilation of existing lake level data reveals that EASM intensity has a complex response to changes in Northern Hemisphere summer insolation on millennial-orbital timescales. Combining precipitation records in central and southern China, the character of rainfall across East Asia during MIS 5 exhibits a dominant tripolar pattern.

Lake desiccation drives carbon and nitrogen biogeochemistry of a sub-tropical hypersaline lake

Lake desiccation drives carbon and nitrogen biogeochemistry of a sub-tropical hypersaline lake

Intensified Warming and Aridity Accelerate Terminal Lake Desiccation in the Great Basin of the Western United States

AbstractTerminal lakes in the Great Basin (GB) of the western US host critical wildlife habitat and food for migrating birds and can be associated with serious human health and economic consequences when they desiccate. Water levels have declined dramatically in the last 100+ years due to diversion of inflows, drought and climate change. Satellite‐derived environmental science data records (ESDRs) from the MODerate‐resolution Imaging Spectroradiometer (MODIS) (snow cover, evapotranspiration (ET) and land surface temperature (LST)), enable a unique approach to evaluate the effects of aridification on terminal lakes and to study their individual vulnerabilities. Surface and air temperatures in the GB are rising dramatically, with a sharp rise in the rate of increase observed beginning around 2011, while the number of days of snow cover is declining especially in the western mountainous part of the GB as exemplified in Mono Basin, California. Rising temperatures coincide with fewer days of snow cover, a decrease of inflow to the lakes and greater evaporation of water from the lakes. MODIS ESDRs show strong and statistically significant increasing surface temperature (LST) in the GB, a reduction in the number of days of snow cover, and mixed results in ET. ET declined slightly in the more arid parts of the GB due to greater moisture restrictions to evaporation from extended drought, while ET increased in the more‐vegetated, wetter, mountainous northeastern parts as temperatures have risen. Severe and costly ecological, human health and economic consequences are expected if the lakes continue to decline as predicted.

Human-environmental interactions and seismic activity in a Late Bronze to Early Iron Age settlement center in the southeastern Caucasus

Long-term human-environmental interactions in naturally fragile drylands are a focus of geomorphological and geoarchaeological research. Furthermore, many dryland societies were also affected by seismic activity. The semi-arid Shiraki Plain in the tectonically active southeastern Caucasus is currently covered by steppe and largely devoid of settlements. However, numerous Late Bronze to Early Iron Age city-type settlements suggest early state formation between ca. 3.2-2.5 ka that abruptly ended after that time. A paleolake was postulated for the lowest plain, and nearby pollen records suggest forest clearcutting of the upper altitudes under a more humid climate during the Late Bronze/Early Iron Ages. Furthermore, also an impact of earthquakes on regional Early Iron Age settlements was suggested. However, regional paleoenvironmental changes and paleoseismicity were not systematically studied so far. We combined geomorphological, sedimentological, chronological and paleoecological data with hydrological modelling to reconstruct regional Holocene paleoenvironmental changes, to identify natural and human causes and to study possible seismic events during the Late Bronze/Early Iron Ages. Our results show a balanced to negative Early to Mid-Holocene water balance probably caused by forested upper slopes. Hence, no lake but a pellic Vertisol developed in the lowest plain. Following, Late Bronze/Early Iron Age forest clear-cutting caused lake formation and the deposition of lacustrine sediments derived from soil erosion. Subsequently, regional aridification caused slow lake desiccation. Remains of freshwater fishes indicate that the lake potentially offered valuable ecosystem services for regional prehistoric societies even during the desiccation period. Finally, colluvial coverage of the lake sediments during the last centuries could have been linked with hydrological extremes during the Little Ice Age. Our study demonstrates that the Holocene hydrological balance of the Shiraki Plain was and is situated near a major hydrological threshold, making the landscape very sensitive to small-scale human or natural influences with severe consequences for local societies. Furthermore, seismites in the studied sediments do not indicate an influence of earthquakes on the main and late phases of Late Bronze/Early Iron Age settlement. Altogether, our study underlines the high value of multi-disciplinary approaches to investigate human-environmental interactions and paleoseismicity in drylands on millennial to centennial time scales.

Arsenic and uranium contamination of Orog Lake in the Valley of Gobi Lakes, Mongolia: Field evidence of conservative accumulation of U in an alkaline, closed-basin lake during evaporation

The shrinkage of inland, alkaline, and saline lakes has caused the elevation of arsenic and uranium concentrations in lake water. However, the chemical reactions associated with these enrichments remain unclear. We conducted a five-year study of the water chemistry of Orog Lake (Mongolia) and the chemical and spectroscopic characteristics of the sediment to determine the geochemical behavior of arsenic and uranium during evaporation. The arsenic and uranium concentrations increased as evaporation caused the lake to shrink. The maximum concentrations of arsenic and uranium exceeded 200 µg/L and 600 µg/L, respectively, when the lake area was the smallest. Comparisons of the monitoring results with predictions of geochemical modeling suggested that some arsenic was removed from the lake water under highly desiccated conditions. Sequential extraction and X-ray absorption near-edge structure analyses showed that ferrihydrite can take up As(V). The accumulation of uranium could be reproduced by considering only evaporation. The conservative behavior of uranium can be explained by the low affinity of U(VI) for carbonate and ferrihydrite at pH > 9 and high dissolved inorganic carbon concentrations. The ubiquitous formation of extremely soluble U-bearing salts after the complete desiccation of inland lakes may thus become a serious threat to limnetic ecosystems.

An operational sociohydrological model to understand the feedbacks between community sensitivity and environmental flows for an endorheic lake basin, lake Bakhtegan, Iran

Over abstraction for agricultural production and droughts in the Bakhtegan basin in southwest Iran has led to decreased lake volumes and has even dried in some years. These problems have occurred in the basin as a result of neglecting the roles that humans have played in lake desiccation. This study developed a socio-hydrological model to understand such dynamic interactions between the economy and community's sensitivity to the environment in the period of 1999 to 2013. The WEAP model was used to simulate the hydrological system that is (bi-directionally) coupled to a society model simulating community sensitivity. A multi-objective optimization algorithm was used to estimate the parameters of the coupled model. The results of the model calibration and validation in estimating the simulated discharges show good performance of the model in simulating observed streamflows (R2 and NSE ranging between 0.73 and 0.99 and 0.31 to 0.99 respectively), agriculture water supplied (R2 and NSE ranging between 0.00 and 0.69 and −7.08 to 0.58 respectively), migration and population (R2 and NSE for migration: 0.29 and 0.63). The results of the integrated model on community response showed that attention to environmental conditions, such as lake levels, was heightened right after the drought events of 2000–2001 and 2008–2010. The effect of the latter event was even accentuated by several human interventions such as operationalization of Sivand and Mollasadra dams and transfer of pristine lands to agriculture. This led to major contraction of the lake. The model interprets that heightened community sensitivity as a result led to public policy dialogue and change. Water was taken away from agriculture and given to the environment leading to temporary lake revival. This was also confirmed by reviewing government decisions in 2011, further validating the value of socio-hydrological models in interpreting feedbacks between community sensitivity and environmental flows.

Compound-specific stable carbon and hydrogen isotope analyses of late-Holocene vegetation and precipitation change at Laguna Los Mangos, Costa Rica

New compound-specific isotope analyses of a sediment core from Laguna Los Mangos in southern Pacific Costa Rica improves understanding of late-Holocene precipitation change in a region with limited paleoprecipitation records that is vulnerable to future climate change. We established paleoprecipitation and paleovegetation records from compound-specific stable hydrogen and carbon isotopic compositions of terrestrially-derived n-alkanes (δ2Halkane and δ13Calkane) to assess paleohydrologic variability and potential linkages to paleoecological change and human activity as revealed by prior analyses of the Los Mangos core. The δ2Halkane values were corrected for isotopic fractionation using pollen counts from the same core. The Los Mangos record extends to 4200 cal yr BP and small increases in δ13C values of C29, +0.6‰, and C31 alkanes, +0.3‰, (δ13CC29, 31) indicate a slight increase in C4 vegetation after initial introduction of maize agriculture to the watershed at ca. 3360 cal yr BP. This slight increase in C4 vegetation is followed by the largest positive carbon isotope excursions in the record, as compared to record averages (δ13CC29 = +3.2‰, δ13CC31 = +5.0‰). Paleohydrologic variability likely influenced vegetation and human activity at Los Mangos. Lake desiccation during the late-Terminal Classic Drought (TCD) resulted in a sedimentary hiatus in the Los Mangos record from ca. 950 to 450 cal yr BP. Positive excursions in comparison to record averages occur for both δ2HC29 and δ2HC31 proxies (δ2HC29 = +25.3 to +13.4‰ and δ2HC31 = +6.5‰) during the middle Little Ice Age (LIA) and indicate drier than average conditions, but there is no evidence of desiccation during this period. Thus, drought conditions during the LIA were apparently not as severe at Los Mangos as during the TCD, possibly because of differing forcing mechanisms for LIA climate that originated, or were more clearly expressed, in the Atlantic basin.

Investigation of climate, land cover and lake level pattern changes and interactions using remotely sensed data and wavelet analysis

Lake Urmia –a hypersaline lake in northwest of Iran- has lost perceptible amount of its waterbody since mid ‘90s. Reasons behind this catastrophe could be categorized as climatic factors and anthropogenic activities. To investigate pattern changes and interactions of the components involved in this dramatic water loss, precipitation (P), discharge (Q), temperature (T), sea surface temperature (SST) alongside satellite images of vegetation cover (VC) from 1990 to 2019 were used for pattern and interaction analysis, including trend and seasonality detection. Owing to the fact that this endorheic lake in extremis is located between East Azerbaijan (EA) and West Azerbaijan (WA) provinces, additionally it was aimed to juxtapose changes in the aforementioned variables assembled from these two provinces. To monitor changes in VC, normalized difference vegetation index (NDVI) time series for two pilot sub-watersheds from EA and WA provinces were calculated using remotely sensed images. Mann-Kendall (MK) trend test revealed that amongst all variables, Q in both sub-watersheds has been intensely decreased in 99% confidence level. Moreover, continuous wavelet transform (CWT) of Q exhibited drastic de-escalations in terms of annual and semi-annual periodicities. VC and urbanization in both sub-watersheds showed significant increasing trends, whereas VC in WA province showed a higher level of trend. Fairly stable P in terms of trend and periodicity alongside intensification in VC concluded intense exploitations of Q which is the other main inflow into this lake. Wavelet coherence transformation (WTC) between all considered variables and Lake Urmia's WL revealed the great impacts of Q, T and SST variables on the lake's WL fluctuations and seasonality. The impact of T and SST on WL fluctuations did not illustrate perceptible changes throughout the study period (i.e., before and after lake's desiccation). The impact of Q on the lake's WL, however, has moved to larger frequency bands with increased phase-lags, and thus, it could be concluded that the intense reduction of the lake's WL is in proportion to intense reduction of rivers discharge to this lake; leaving transparent traces of anthropogenic impacts on Lake Urmia's tragedy.

Water management or megadrought: what caused the Chilean Aculeo Lake drying?

The Aculeo Lake is an important natural reservoir of Central Chile, which provides valuable ecosystem services. This lake has suffered a rapid shrinkage of the water levels from year 2010 to 2018, and since October 2018, it is completely dry. This natural disaster is concurrent with a number of severe and uninterrupted drought years, along with sustained increases in water consumption associated to land use/land cover (LULC) changes. Severe water shortages and socio-environmental impacts were triggered by these changes, emphasizing the need to understand the causes of the lake desiccation to contribute in the design of future adaptation strategies. Thereby, the Water Evaluation and Planning (WEAP) hydrological model was used as a tool to quantify the water balance in the catchment. The model was run under a combination of three land use/land cover and two different climate scenarios that sample the cases with and without megadrought and with or without changes in land use. According to the results, the main triggering factor of the lake shrinkage is the severe megadrought, with annual rainfall deficits of about 38%, which resulted in amplified reductions in river flows (44%) and aquifer recharges (24%). The results indicate that the relative impact of the climate factor is more than 10 times larger than the impact of the observed LULC changes in the lake balance, highlighting the urgent need for adaptation strategies to deal with the projected drier futures.

Restoration perceptions and collaboration challenges under severe water scarcity: the Aculeo Lake process

A governmental watershed collaborative process in Aculeo, a semi‐endorheic 149 km2 sub‐basin in Chile, debated options for the water scarcity problems they were facing, including their lake desiccation. However, instead of joining forces, discussions around the possibility of recovering the lake generated further conflicts, revealing that it was not a goal shared by all. In this article, we explore the different perceptions and reasons that influenced preferences on restoring or rehabilitating the Aculeo Lake. By collecting, coding, and comparing before and during collaborative process perceptions, we analyzed the perceptions of the proposed Aculeo Lake rehabilitation that are shared among both those who oppose and those who support it. Results indicate that the underlying disagreement was primarily due to differences in shore property rights and lake access, which was also linked to different opinions about land uses in the territory. This research displays how both values and understandings of problems, along with history of a site, can impact stakeholders' restoration preferences and turn into a collaboration challenge.