River Damming Research Articles

Does a hydropower reservoir cascade really harm downstream nutrient regimes

River damming is believed to largely intercept nutrients, particularly retain more phosphorus (P) than nitrogen (N), and thus harm primary productivity, fishery catches, and food security downstream, which seriously constrain global hydropower development and poverty relief in undeveloped regions and can drive geo-political disputes between nations along trans-boundary rivers. In this study, we investigated whether reservoirs can instead improve nutrient regimes downstream. We measured different species of N and P as well as microbial functions in water and sediment of cascade reservoirs in the upper Mekong River over 5 years and modelled the influx and outflux of N and P species in each reservoir. Despite partially retaining total N and total P, reservoirs increased the downstream flux of ammonium and soluble reactive phosphorus (SRP). The increase in ammonium and SRP between outflux and influx showed positive linear relationships with the hydraulic residence time of the cascade reservoirs; and the ratio of SRP to dissolved inorganic nitrogen increased along the reservoir cascade. The lentic environment of reservoirs stimulated algae-mediated conversion of nitrate into ammonium in surface water; the hypoxic condition and the priming effect of algae-induced organic matter enhanced release of ammonium from sediment; the synergy of microbial phosphorylation, reductive condition and sediment geochemical properties increased release of SRP. This study is the first to provide solid evidence that hydropower reservoirs improve downstream nutrient bioavailability and N-P balance through a process of retention-transformation-transport, which may benefit primary productivity. These findings could advance our understanding of the eco-environmental impacts of river damming.

Hypoxia and its feedback response to algal blooms and CH4 emissions in subtropical reservoirs

Anthropogenic nutrient input stimulates surface eutrophication and algal blooms and thus exacerbates oxygen depletion and hypoxia in aquatic ecosystems. However, existing studies have paid little attention on the understanding of the feedback relationships among oxygen consumption, algal succession and greenhouse gas effect after river damming, particularly in Three Gorges Reservoir. This field work investigated the thermal stratification, water quality and phytoplankton in four tributaries (Pengxi Bay (PXB), Daning Bay (DNB), Shennong Bay (SNB), and Xiangxi Bay (XXB)) of the Three Gorges Reservoir (TGR) in spring (April 25-28, 2022), and explored the drivers of hypoxia and its feedback response to algal blooms and methane (CH4) emissions. The results showed that during the observation period, DO, thermal stratification, and algal blooms were more severe in PXB. The high Chemical Oxygen Demand (CODMn) (11.27 mg•L-1) and Dissolved Organic Carbon (DOC) content (7.56 mg•L-1) in PXB were the main causes of the progressive hypoxia. Furthermore, stronger density stratification in PXB inhibited the vertical supply of DO and accelerated bottom hypoxia. But the downslope density current replenished bottom DO in the upper reaches of the DNB, SNB, and XXB. The CH4 concentration was generally higher in hypoxia zone, especially in where cyanobacteria are the dominant species (eg., PX03 and PX04). Dam construction led to the succession of algal-dominant species, exerting a significant influence on the river carbon cycle. The expansion of cyanobacterial blooms and the consequence of metabolic substrates increase are gradually increasing oxygen deprivation, even hypoxia, and enhancing CH4 production in rivers. These findings suggest that the succession of algal-dominant species caused by river damming has a pronounced positive feedback effect on reservoir hypoxia processes and greenhouse effect.

Elaboration and application of the nested multi-coupling model test system for an artificial dam seepage simulation under combined action of dynamic and static loads

Outdated coal mining technologies involve considerable mine water resource waste. For coal mines located in water-starved western regions of China, this jeopardizes the sustainable coal mining development, local eco-environment, and agricultural production. Coal mine underground reservoirs furnish conservation and cyclic utilization of water resources in the coal mining process. The weakest links of underground reservoirs are artificial dams that are prone to frequent occurrence of water seepage and instability failures. Aiming to explore the deformation rules of artificial dams under fluid–solid coupling action, this study developed a nested multi-coupling test system comprising a model shelf, a mine pressure simulation device, a water pressure simulation device, and a monitoring system, The maximum size of the model shelf is 1400 mm * 1300 mm * 200 mm. The mine pressure simulation device was composed of static-load and vibration-load oil cylinders of various sizes. A servo motor mainly controlled the water pressure device; with a water pressure sensor and high-precision flowmeter, water pressure could be accurately adjusted. By taking the underground reservoir in the Wulanmulun Coal Mine as an example, the deformation failure characteristics of the MB-1 dam under fluid–solid coupling conditions were simulated to validate the reasonability and feasibility of the developed system. The obtained experimental results indicated that the artificial dam damage was induced by increased mine pressure, leading to shear compression failure. The artificial dam underwent plastic deformation at a water pressure of 11.43 kPa, accompanied with the generation of microfractures, which rapid propagation under vibration loading violated the dam’s stability.

River dams, free stretches and migratory fish species: a review of the state of the art in the state of São Paulo, Brazil.

Population growth combined with the need for electrical energy resulted in the construction of hundreds of hydroelectric plants in the state of São Paulo, Brazil. The consequence of these interventions was the fragmentation of rivers, forming barriers, that hinder the mobility of migratory fish species, generating an impact on the life cycle of these species, especially about movement between breeding and feeding areas. For this reason, this article aimed to evaluate the state-of-the-art knowledge regarding dams, free stretches, and migratory species in the three main river basins of the state of São Paulo and its tributaries. Through a systematic review from 2003 to 2023, 89 articles were obtained, 48 of which were about dams, 5 which addressed fish transposition systems, and 36 portraying migratory species. In the first half, research focused more on the impacts of dams on fish fauna, while in the second half of the period studied, studies of migratory fish were dominant. Most research was conducted in the main rivers, with few in the tributaries. Finally, 16 migratory species, considered long-distance, were studied, the most studied being P. lineatus, P. maculatus, L. friderici, M. obtusidens and S. hilarri and the ones that occurred most frequently in rivers are Prochilodus lineatus, Pimelodus maculatus, Megaleporinus obtusidens and Salminus hilarii. Therefore, we recommend maintaining the natural flow regime that still exists in the main rivers and tributaries of the state of São Paulo, to maintain healthy populations of the inventoried species.

Assessment of flood controlling ability of hypothetical flood control dams by HEC-HMS model in catchment area of Koyna Dam in India

Assessment of flood controlling ability of hypothetical flood control dams by HEC-HMS model in catchment area of Koyna Dam in India

Water quality in the reservoirs of seasonal river dams

Water quality in the reservoirs of seasonal river dams

Macro-micro crack and damage evolution characteristics of concrete: After the action of acidic drying-saturation cycle

Repeated saturation and drying of acidic mine water have a major influence on the mechanical properties and stability monitoring of artificial dams (concrete walls) in underground reservoirs. A uniaxial compression acoustic emission (AE) monitoring test was conducted to quantify the evolution characteristics of micro cracks in concrete. In addition, the evolution characteristics of macro cracks during sample failure were quantitatively analyzed by fractal dimension theory and Image-Pro. Finally, the damage constitutive model was established and the damage evolution law was studied. The results of the study showed that the percentage of micro shear cracks in dry samples exhibited a decreasing and then increasing trend during the loading stage before the uniaxial compressive strength (UCS). However, after the acidic drying-saturation cycle (ADSC), this percentage of concrete showed an increasing trend. As the number of drying-saturation cycles increases or the pH decreases, the fractal dimension, total length, and area of the macro cracks also increase. The damage constitutive model, based on ADSC and loading conditions, works well. After the ADSC, the concrete sample will have three damage stages. Additionally, the strain at entry into each stage increases. Expansion and shrinkage of hydration products and chemical damage due to ion exchange are the mechanisms that change the mechanical properties and the macro-micro crack evolution pattern of concrete after ADSC.

Status of the Critically Endangered gharial Gavialis gangeticus in the upper Ghaghara River, India, and its conservation in the Girwa–Ghaghara Rivers

AbstractThe gharial Gavialis gangeticus is a Critically Endangered crocodilian endemic to the Indian subcontinent. Habitat modification by river damming and water extraction has caused a severe decline in its population. The status of the gharial is known within protected areas, but there have been few surveys for this species in unprotected areas. In Katerniaghat Wildlife Sanctuary, a breeding gharial population in Girijapuri Barrage Reservoir has low recruitment, and it has been hypothesized that yearlings disperse downstream into the unprotected Ghaghara River when the barrage gates are opened. We surveyed a 100-km stretch of the Ghaghara River from the Girijapuri Barrage to Chahlari Ghat, observing a total of 84 gharials, including a high proportion of juveniles. A survey in 2021 from Chahlari Ghat to Ayodhya observed 174 gharials, giving a combined total of 258 gharials in a 219-km stretch of the Ghaghara River for the two surveys. Together, these findings confirm the presence of a significant population of gharials in the Ghaghara River. We recommend the adoption of an integrated approach, involving government agencies and local communities along the river, to conserve the protected Girwa–Kaudiyala Rivers and the unprotected Ghaghara River for gharial conservation and recovery. Such a programme will need to tackle the threats facing the gharial and establish baseline data and long-term monitoring protocols for freshwater species conservation in this river system.

A review of conservation status of freshwater fish diversity in China.

China harbors a high species diversity of freshwater fishes not shared with any of its neighboring nations. Freshwater fish diversity in the country has been under severe threat from human activities over the past decades, thus conservation freshwater fishes and ecosystems is urgently needed. To accumulate baseline data for guiding protection actions, the third red list assessment of Chinese freshwater fishes was carried out. Among Chinese freshwater fishes assessed, there are 355 at-risk species (22.3% of the total), including 69 ranked as Critically Endangered, 97 as Endangered, and 189 as Vulnerable. Two species are classified as Extinct and one as Regionally Extinct. China's threat level seems to be lower than the known average level found in the IUCN's global assessment of freshwater fishes, but this is an artifact of a high rate of species classified as Data Deficient. Conservation of freshwater fishes is presently facing a grim situation in China. Imperilment of Chinese freshwater fishes is primarily attributed to habitat loss and degradation arising from human perturbations, particularly river damming. Despite the adoption of protected areas setting up, captive breeding and release, and a fishing moratorium, conservation efforts for freshwater fishes are compromised by disproportional attention in China's biodiversity conservation, baseline data deficiency, insufficiently designed protection networks, and inefficient or inadequate implementation of conservation strategies. To achieve the objectives of Chinese freshwater fish conservation, it is proposed to conduct a national-scale survey of fish diversity and reassess their at-risk status, develop systematic conservation planning of freshwater fish diversity and ecosystems, prioritize strategies for protected areas development, perform genetic-based captive breeding for releasing in concert with other protection actions, and implement flexible fishing moratorium strategies in different water bodies.

River Damming Impacts on Fish Habitat and Associated Conservation Measures

AbstractRiver damming has brought great benefits to flood mitigation, energy and food production, and will continue to play a significant role in global energy supply, particularly in Asia, Africa, and South America. However, dams have extensively altered global river dynamics, including riverine connectivity, hydrological, thermal, sediment and solute regimes, and the channel morphology. These alterations have detrimental effects on the quality and quantity of fish habitat and associated impacts on aquatic life. Indeed, dams have been implicated in the decline of numerous fishes, emphasizing the need for effective conservation measures. Here, we present a global synthesis of critical issues concerning the impacts of river damming on physical fish habitats, with a particular focus on key fish species across continents. We also consider current fish conservation measures and their applicability in different contexts. Finally, we identify future research needs. The information presented herein will help support sustainable dam operation under the constraints of future climate change and human needs.

Creating Sustainable Climate Change Havens for Migrating Populations in the United States and Other Global Sites

A model for constructing sustainable Climate Change Haven communities in appropriate areas of the United States and globally is presented. The model proposes the construction of walkable communities of 20,000 to 30,000 residents with electricity provided by hydropower generators and biofuel combustion. The remediation of surface-mined areas using switchgrass and flood control dams to redirect excess rainfall will be required in some areas. This model also addresses the multiple social and cultural considerations required to resettle groups of migrants in Climate Change Haven communities, together with the preparation and preservation of nearby farmland for feeding the community.

Isotopic niches of diadromous fishes inform on interspecific competition in an obstructed catchment

Competition arises when species share a limited resource, but this can be avoided through niche partitioning. Despite the large body of literature on diadromous fishes, very few studies have focused on niche partitioning when competing for resources. Diadromous fishes are suffering a global decline throughout their range in part due to their peculiar life history traits as they migrate from the sea to freshwater to spawn or the reverse. They are particularly sensitive to river fragmentation induced by barriers. Dams for instance are expected to alter the spatial distribution and resource exploitation of diadromous fishes as well as other organisms. Here, we studied the ecological niche of six taxa of diadromous fishes, temporally co-occurring in the same land–sea continuum obstructed by two river dams. We used Bayesian mixing models run on C and N isotopes to infer the various habitats used and the origin of the trophic carbon in muscle and scale tissues of diadromous fishes. Results showed that the sub-adults of Anguilla anguilla, juveniles of Petromyzon marinus, and Salmo trutta exploit mainly the freshwater, or marine part for adults of Lampetra fluviatilis, whereas juveniles of Platichthys flesus and Mugilidae use all the habitats of the land–sea continuum. In the freshwater habitat, the microphytobenthos and biofilm are the main sources of carbon used, while in the marine habitat, the basal carbon sources are more diverse. The analyses of niche overlaps between diadromous fishes demonstrate that the widest isotopic niches, observed for A. anguilla and P. flesus, also have more impact within the community. Results are discussed in terms of intra- and interspecific competition between these diadromous fishes and their generalist/specialist strategies in an obstructed catchment.

Ecological impacts of dam construction on epilithic diatom communities in estuaries: A case study of the Korean peninsula

This study, spanning 2016 to 2018, investigated diatom distribution in 324 Korean Peninsula estuaries, emphasizing the ecological impact of artificial dams. Examining environmental and biological variables, we focused on dam construction. OPEN estuaries exhibited higher urban/forest land cover and had more alkaline, saline, conductive, and oxygen-rich water. In CLOSE estuaries, agricultural farmland and nitrogen compound concentrations were higher. Dams in CLOSE estuaries correlated with lower pH, salinity, electrical conductivity, and dissolved oxygen. Regional variations were evident, with WEST OPEN estuaries showing higher salinity, turbidity, chemical oxygen demand, and total phosphorus. SOUTH estuaries displayed intermediate characteristics, while EAST OPEN estuaries had higher dissolved oxygen but lower temperature and turbidity.Diverse epilithic diatoms were identified, with OPEN estuaries displaying greater species richness, primarily dominated by Nitzschia inconspicua Grunow. CLOSE estuaries, conversely, exhibited higher richness with a different subdominant species. Indicator species analysis revealed taxa specific to estuaries and sea areas, with CLOSE ones exhibiting lower salinity and higher nitrogen/phosphorus concentrations. Nitzschia inconspicua dominated all estuaries, but subdominant species varied; N. fonticola (Grunow) Grunow in OPEN, N. paleaceae (Grunow) Grunow in CLOSE. CLOSE estuaries had higher species richness. In the West Sea, turbidity and TP levels affected diatom growth, with dams exacerbating turbidity and potentially disrupting the food chain.Results underscored intricate interactions between dams, land use, and diatom communities, offering foundational data for ecosystem management and biodiversity conservation in Korean Peninsula estuaries. Understanding the ecological consequences of artificial dams on diatom distribution is crucial for preserving estuarine health. Future research is recommended to explore additional factors influencing these ecosystems, particularly focusing on various organisms in West Sea estuaries for effective ecosystem management and conservation.

Hydrological regimes and water quality variations in the Yangtze River basin from 1998 to 2018

Understanding the long-term variations in basins that undergo large-scale hydroelectric projects is crucial for effective dam operation and watershed management. In this study, comprehensive analyses were conducted on a dataset spanning over 20 years (1998–2018) of hydrological regime and physicochemical parameters from the Yangtze River basin to evaluate the potential impacts of the Three Gorges Dam. Water level significantly increased from 128.75±58.18 m in 2002 to 136.78±55.05 m in 2005, and the mean flow velocity significantly decreased from 2004 to 2010. However, no significant change in the flow was observed in the basin. Meanwhile, remarkable fluctuations in physicochemical parameters, including dissolved oxygen, chemical oxygen demand, conductivity, hardness, and alkalinity, were mainly observed during impoundment (2003–2009). After that, the above parameters tended to stabilize, and some even returned to their original levels. The dam's retention effect significantly reduced the suspended solids (SS) in both up- and downstream, to only one-third of the pre-operation level. And total phosphorus and chemical oxygen demand also significantly decreased with the decline of SS. Particularly, ammonium also showed a significant downward trend, with the up- and downstream of the dam falling by 36.8 % and 26.1 %, respectively. However, the increasing total nitrogen (7.5 % and 20.0 % up- and downstream of the dam, respectively) still threatened the water quality of the basin, especially in the estuaries. Additionally, the significant decline in dissolved oxygen downstream (from 8.53±1.08 mg/L to 8.11±1.36 mg/L) also exacerbated the hypoxia in the Yangtze River estuary. The results demonstrated the long-term impact of the construction of the Three Gorges Dam on the environmental elements of the Yangtze River basin, which provides reference data and guidance for the construction of big dams in major rivers in the future.

Geophysical and Geochemical Pilot Study to Characterize the Dam Foundation Rock and Source of Seepage in Part of Pensacola Dam in Oklahoma

Pensacola Dam, operated by the Grand River Dam Authority (GRDA), is a multiple-arch buttress dam constructed in 1940. The dam has little or no existing geophysical reports on the integrity of the dam foundation rock and even less knowledge at depth. Visual inspection indicated evidence of seepage at some arches of the dam. As a pilot study, we conducted a suite of geophysical surveys inside two arches (Arch-16 and Arch-17) and a part of the downstream berm to characterize the dam foundation rock, delineate seepage zones, and identify the most appropriate geophysical methods for temporal monitoring of the dam’s conditions. The geophysical methods included electrical resistivity tomography (ERT), self-potential (SP), multichannel analysis of surface waves (MASW), compressional (P)-wave refraction, and shear (S)-wave reflection. Water samples were collected for geochemical analysis to investigate the source of the seepage flow inside Arch-16. The geophysical results characterized the dam foundation rock into an unsaturated limestone and chert overlying a water-saturated limestone and chert. The ERT profiles indicated that groundwater is rising inside the arches and significantly dropping under the downstream berm, which can be due to the uplift pressure beneath the dam base. Zones of high seepage potential were detected near the buttress walls of the two surveyed arches, which may be related to previous blasting, excavation of the dam foundation, concrete placement, or improper grouting. The geochemical analysis of water samples taken from the artesian wells inside Arch-16 and the Grand Lake revealed different chemical compositions, suggesting that the source of water could be a mixture of groundwater and lake water or lake water interacting with rock and reaching the surface through fractures; however, more sampling and further analysis are required to ascertain the source of the seeps. This study showed that the ERT, SP, and S-wave reflection methods have effectively characterized the dam foundation rock and seepage zones beneath the arches. The study provided a better understanding of the conditions of the dam foundation rock, evaluated the utilized geophysical methods, and determined the optimum geophysical methods that can be used for the characterization and monitoring of the subsurface conditions along the entire length of the dam. In this study, we have demonstrated that the integration of effective geophysical surveys and geochemical analysis yielded optimum results in solving a complex dam safety problem. This strategy promotes the best practice for dam safety investigation.

Predicting the likelihood of gas bubble trauma in fishes exposed to elevated total dissolved gas in the lower Clark Fork River, Idaho

AbstractObjectiveGas bubble trauma (GBT) can occur in fish when water becomes supersaturated with gases, with effects ranging from minor tissue damage to death. Laboratory studies suggest that fish exposure to elevated total dissolved gas (TDG) at depths that compensate for gas supersaturation can result in reduced GBT incidence and that different fish species exhibit varying susceptibility to GBT. Elevated TDG levels associated with spill at Cabinet Gorge Dam in the lower Clark Fork River, Idaho, facilitated describing the incidence and severity of GBT, variables that affect GBT incidence, and the probability of observing GBT in different fish species.MethodsTotal dissolved gas and GBT data were collected during the typical spill period (i.e., April–July) in 2000, 2006, 2008, and 2017–2021.ResultA total of 6985 fish was examined for GBT at TDG of 101–137% saturation. Incidences of GBT varied with TDG levels, and the greatest incidence of GBT was typically observed near the date with peak daily mean TDG. Logistic regression models indicated that the probability of observing GBT was affected by TDG exposure and temperature but not length. The probability of observing GBT on fish was < 0.01 when 7‐day mean TDG was 110% saturation and < 0.04 when 7‐day mean TDG was 120% saturation. The models also indicated that the probability of observing GBT at a given TDG value differed between fish species.ConclusionWe suggest that species‐specific behavior and habitat composition in the sampled area (i.e., access to compensatory depths and locations with less TDG) were factors in our observations. We advocate that fisheries managers use a similar process to develop site‐ and species‐specific GBT probability curves where elevated TDG is an issue. These site‐specific curves can help managers evaluate the potential for population‐level effects to fisheries and need for TDG reduction or mitigation actions.

Dam operation using satellite data and hydrological models: the case of Roseires dam and Grand Ethiopian Renaissance Dam in the Blue Nile River

ABSTRACT The unexpected drop of the Blue Nile water in July 2020, attributed to the sudden closure of the Grand Ethiopian Renaissance Dam (GERD) during the first filling in 2020, significantly interrupted the water supply for Khartoum, Sudan. This incident pursued using satellites and hydrological models to estimate inflows into Roseires dam. A hydrological model was developed to predict GERD inflows, while reservoir levels were extracted from Sentinel-1, -2 and Jason-3. A water balance model was developed to predict GERD releases and the dates of overtopping during subsequent fillings events. The study demonstrates the effectiveness of satellite data and models for transboundary reservoir management.

Impacts of artificial dams on terrestrial water storage changes and the Earth's elastic load response during 1950–2016: A case study of medium and large reservoirs in Chinese mainland

The construction of dams for intercepting and storing water has altered surface water distributions, land-sea water exchanges, and the load response of the solid Earth. The lack of accurate estimation of reservoir properties through the land surface and hydrological models can lead to water storage simulation and extraction errors. This impact is particularly evident in many artificial reservoirs in China. The study aims to comprehensively assess the spatiotemporal distribution and trends of water storage in medium and large reservoirs (MLRs) in Chinese mainland during 1950–2016, and to investigate the gravity, displacement, and strain effects induced by the reservoir mass concentration using the load elasticity theory. In addition, the impoundment contributions of MLRs to the relative sea level changes were assessed using a sea-level equation. The results show impoundment increases in the MLRs during 1950–2016, particularly in the Yangtze River (Changjiang) and southern basins, causing significant elastic load effects in the surrounding areas of the reservoirs and increasing the relative sea level in China's offshore. However, long-term groundwater estimation trends are overestimated and underestimated in the Yangtze River and southwestern basins, respectively, due to the neglect of the MLRs impacts or the uncertainty of the hydrological model's output (e.g., soil moisture, etc.). The construction of MLRs may reduce the water mass input from land to the ocean, thus slowing global sea level rise. The results of the impact of human activities on the regional water cycle provide important references and data support for improving the integration of hydrological models, evaluating Earth's viscoelastic responses under long-term reservoir storage, enhancing in-situ and satellite geodetic measurements, and identifying the main factors driving sea level changes.

Deconstructing dams and disease: predictions for salmon disease risk following Klamath River dam removals

The health of fish populations and the river systems they inhabit have broad ecological, cultural, recreational, and economic relevance. This is exemplified by the iconic anadromous salmonid fishes native to the West Coast of North America. Salmon populations have been constrained since the mid nineteenth century by dam construction and water reallocation. In the Klamath River (Oregon and California, USA), a series of dams built in the early-mid 20th century cut the basin in two and blocked anadromous fish access to more than 600 river kilometers. This dramatic loss of habitat, coupled with infectious diseases and resulting epizootics, have impacted the wellbeing of these salmonid populations. In 2023-2024, the Klamath River will undergo the largest river restoration project in US history. Removal of the four lowermost dams will cause profound physical changes to the river, including flow, water temperature, and channel geomorphology. The dam removals will reconnect the lower and upper portions of the basin, and provide fish passage after a century of segregation. Reestablishment of upstream and downstream fish movements will also alter the occupancy and abundance of the salmonid hosts and their pathogens. The increased habitat availability and longer migration routes will increase duration of pathogen exposure and potential impacts on juvenile survival and adult pre-spawn mortality. However, restoration of more natural flow and sediment regimes will decrease overall fish disease risk by disrupting complex parasite life cycles. To better understand these multifarious, competing factors, we review the salmonid species in the Klamath River, and provide an overview of their historical pathogen challenges and associated diseases and use this as a framework to predict the effects of dam removals on disease dynamics. Our review and predictions are a synthesis of expertise from tribal biologists, fish health specialists and fish biologists, many of whom have lived and worked on the Klamath River for decades. We conclude with recommendations for expansion of current pathogen monitoring and research efforts to measure changes in host-pathogen dynamics basin-wide.

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.