Wetland Water Depth Research Articles

Uncovering extensive populations of the ‘threatened’ Black Crowned Cranes in Gambella, Ethiopia

A reliable assessment of the population size of threatened species is crucial for making informed decisions about their conservation and management. However, there is a lack of comprehensive knowledge on the population of the eastern Black Crowned Crane (Balearica pavonina ceciliae), which is globally recognized as a threatened taxon experiencing a declining population trend. Here, we investigated the density, abundance and factors that influence flock size in the wetlands of the Gambella region in Ethiopia. We used line transects to collect data during dry and wet seasons. Population density and abundance were estimated using DISTANCE software, whereas factors influencing crane flock size were evaluated using a generalized linear model. We found that crane density ranged from 444 to 965 birds per sq km in the dry season and from 62 to 105 individuals per sq km in the wet season. We estimated that the population size within the designated survey areas as 7634 during the dry season and 866 during the wet season. Furthermore, for the broader survey region that encompasses permanent wetlands, the estimated population ranged from 9138 to 19,849 individuals in the dry season and from 1272 to 2166 individuals in the wet season. We found that grazing intensity and proximity to woodlands and rivers had significant positive impacts on crane flock size, whereas an increase in wetland water depth and grass height remarkably reduced flock size. As a result, wetland habitat degradation-related problems are not currently a threat to cranes in this region, but are likely to increase in the future due to large-scale agricultural expansion. The crane population size we estimated in Gambella is high, three to four times higher than the estimate from the entirety of Ethiopia. Our research underscores the global significance of Gambella wetlands as an important habitat for cranes. However, to obtain an accurate population estimate in this region, it is imperative to include seasonal wetlands, savannah grasslands, farmlands and the extended wetlands of South Sudan, which are hydrologically connected to the wetlands of Gambella region. To achieve this, comprehensive surveys and estimations should incorporate various techniques, such as aerial surveys, satellite telemetry, and high-resolution satellite imagery.

Evaluating damming effect on eco-hydrological alteration in river and wetland using indicators of hydrological alteration

Present work successfully examined the damming impact on the eco-hydrological conditions of the river and wetland. The study found that monthly mean discharge was attenuated by 1.61 to 57% after damming. About 28.57 to 100% flow failure rate was found in the post-dam period and a moderate to the high degree of negative hydrological alteration (HA) for different IHA groups was identified. The flow failure rate in the river was >70% in most of the months while wetland water depth failure rates were 43% in pre-dam to 71% in post-dam, and a low and high negative degree of HA was observed over 20% and 9% of wetland areas respectively during post-monsoon season. The damming effect was found more intensive in the river than in wetlands. The eco-hydro deficit was recorded, which is an indication of growing ecological distress. The current result is used for river and wetland restoration planning.

Using biodiversity response for prioritizing participants and service provisions in a payment-for-water-storage program in the Everglades basin

Hydrological changes can lead to biodiversity responses that are complex and challenging to quantify. We present a framework that uses biodiversity as a criterion to address “where to buy” and “how much to buy” in a payment-for-environmental-services (PES) program focused on water storage service in the Everglades basin, USA. The PES program was designed to pay for added water storage on private cattle ranchlands by raising the spillage level in drainage control structures to reduce surface flows. We predicted that increased hydration of previously drained wetlands would benefit biodiversity, a previously unquantified but desirable co-benefit of the original program, and that a PES program offering bundled services (e.g., storage and biodiversity) can better achieve restoration goals. We quantified desirable biodiversity services (abundance of native flora and fauna such as cover of wetland and forage plants, and abundance of fishes, amphibians, and macroinvertebrates), dis-services (e.g., abundance of invasive plants and mosquitos), and hydrologic signatures (e.g., wetland water depth, inundation area and duration) at four ranches to develop eco-hydrological relationships (models) between hydrological changes and biodiversity responses. Next, a hydrologic model (MIKE-SHE/MIKE-11) was used to predict surface and subsurface water levels and flows and resulting wetland hydrologic signatures for 13 water storage alternatives on the ranches, which were used as example PES proposals. A decision-support-system (DSS) was developed to integrate (i) storage predicted by the hydrologic model, (ii) biodiversity responses predicted by eco-hydrologic models, and (iii) a user-defined preference scheme to assign importance weights to storage, biodiversity, and implementation cost. The DSS calculated a cumulative score for ranking PES proposals. By considering desirable services and dis-services, stakeholders can decide on their preferred level of services, e.g., buyer(s) may settle for less storage if there is a gain in desirable biodiversity. The DSS can identify trade-offs among services, helping stakeholders negotiate.

Water level changes in Lake Erie drive 21st century CO2 and CH4 fluxes from a coastal temperate wetland

Wetland water depth influences microbial and plant communities, which can alter the above- and below-ground carbon cycling of a wetland. Wetland water depths are likely to change due to shifting precipitation patterns, which will affect projections of greenhouse gas emissions; however, these effects are rarely incorporated into wetland greenhouse gas models. Seeking to address this gap, we used a mechanistic model, ecosys, to simulate a range of water depth scenarios in a temperate wetland, and analyzed simulated predictions of carbon dioxide (CO2) and methane (CH4) fluxes over the 21st century. We tested our model using eddy covariance measurements of CO2 and CH4 fluxes collected at the Old Woman Creek National Estuarine Research Reserve (OWC) during 2015 and 2016. OWC is a lacustrine, estuarine, freshwater, mineral-soil marsh. An empirical model found that the wetland water depth is highly dependent on the water depth of the nearby Lake Erie. Future wetland surface water depths were modeled based on projection of Lake Erie's water depth using four separate NOAA projections, resulting in four wetland water-depth scenarios. Two of the four 21st century projections for Lake Erie water depths used in this study indicated that the water depth of the wetland would remain nearly steady; however, the other two indicated decreases in the wetland water depth. In our scenario where the wetland dries out, we project the wetland's climatological warming effect will decrease due to smaller CH4 fluxes to the atmosphere and larger CO2 uptake by the wetland. We also found that increased water level can lower emissions by shifting the site towards more open water areas, which have lower CH4 emissions. We found that decreased water depths would cause more widespread colonization of the wetland by macrophyte vegetation. Using an empirical relationship, we also found that further drying could result in other, non-wetland vegetation to emerge, dramatically altering soil carbon cycling. In three of our four projections, we found that in general the magnitude of CO2 and CH4 fluxes steadily increase over the next 100 years in response to higher temperatures. However, in our driest simulations, we projected a different response due to increased oxidation of soil carbon, with CH4 emissions decreasing substantially from an annual cumulative peak of 224.6 to a minimum of 104.7 gC m−2 year−1. In that same simulation, net cumulative flux of CO2 changed from being a sink of 56.5 gC m−2 year−1 to a source of 369.6 gC m−2 year−1 over the same period, despite a temperature increase from 13.7 °C to 14.2 °C. This temperature shift in our other three cases with greater water depths increased the source strength of CH4 and the sink strength of CO2.We conclude that the magnitude of wetland greenhouse-gas fluxes depended on the water depth primarily as it affected the areal percentage of the wetland available for plant colonization, but dramatic decreases in water depths could cause significant reductions in the wetland CH4 fluxes, while simultaneously altering the wetland vegetation.

인과순환구조 분석을 활용한 지속가능한 수변도시의 그린 인프라 도입 및 식재기반 계획 : 부산 에코델타시티를 중심으로

Busan Eco-Delta city is being developed under the paradigm of eco-friendly waterfront cities with goals such as sustainable development, ecosystem service improvement, and climate change response, etc. To do this, it is necessary to analyze the key variables that appear in common in recognition of the planting base environment and introduction of green infrastructure and to analyze the integrated system. Therefore, the purpose of this study is to analyze the causal loop structure to construct planting base and introduce green infrastructure in realizing a sustainable waterfront city. First, the causal loop structure of the planting base environment according to tidal-flat soil, mountain soil, and dredged sediment was analyzed using system thinking in system dynamics methodology. As a result of integrating individual causal loop structures, key variables of the planting base environment were soil hardness, organic matter in soil, soil pH, soil salinity, and plants growth variables. Second, when introducing green infrastructure (urban forests, wetlands, grasslands) to the planting base, constraints were derived and presented as a causal loop structure. In urban forests, the values of soil hardness, slope, soil pH, soil salinity, soil drainage, and plant growth should be taken into consideration. In wetlands, variables of soil hardness, soil permeability, soil moisture, wetland water level fluctuation, and wetland water depth should be taken into consideration. In grasslands, consideration of the variables of soil hardness, soil drainage and permeability, soil pH, and plant growth needed. The green infrastructure introduced in this study is important in that it can respond to climate change as well as environmental pollution. It is expected that the results of this study can be used as the basis for a green infrastructure plan in the process of developing Busan Eco-Delta city.

Heavy metal pollution and potential ecological risk assessment for surficial sediments of Deepor Beel, India

The present study has been conducted for three objectives for the assessment of sediment pollution loadings and their ecological risk. Firstly, the hierarchical clustering of the raw sediment dataset was carried out, which categorized the sampling locations into three statistically significant clusters, depending on their similarities in behaviours. Clusters 1, 2, and 3 corresponded to high, moderate, and low pollution sites, respectively. The principal component analysis was then carried out on the dataset for three different seasons; pre-monsoon, monsoon and post-monsoon respectively, which showed significant temporal changes in the pollution sources. Various indices such as contamination factor, pollution load index, enrichment factor, and the geo-accumulation index showed that the wetland is most affected in the post-monsoon season as compared to other seasons. At the same time, monsoon remains the best. This was attributed to the significant increase in the wetland's water depth during the monsoon, coupled with the rise in precipitation capacity during the post-monsoon. Secondly, the potential ecological risk due to the contaminants displayed that the post-monsoon period has the greatest number of sites under the moderate risk category. In contrast, all the sites during the monsoon attributed to low risk. Also, Cd was found to be the primary contributor to ecological risk. Finally, chemical speciation analyses of all the heavy metals were conducted to determine their available forms in the sediment column. Cr, Mn, and Mg were observed to have a profoundly negative impact on aquatic ecology (available in F1 fraction in higher percentages). While Fe was predominant in reducible (F3) form, Cd was found to have equal contributions in reducible and oxidizable (F3 and F4, respectively) forms. Cu and Pb displayed typical complex characteristics of all the fractions in almost equal proportions. The results of the study indicated that although the anthropogenic interventions to the wetland have not been significant till yet, as far as the sediment contamination is concerned, it would be too late if swift and appropriate measures are not taken for restricting future probable contaminations.

Adaptation Tipping Points of a Wetland under a Drying Climate

Wetlands experience considerable alteration to their hydrology, which typically contributes to a decline in their overall ecological integrity. Wetland management strategies aim to repair wetland hydrology and attenuate wetland loss that is associated with climate change. However, decision makers often lack the data needed to support complex social environmental systems models, making it difficult to assess the effectiveness of current or past practices. Adaptation Tipping Points (ATPs) is a policy-oriented method that can be useful in these situations. Here, a modified ATP framework is presented to assess the suitability of ecosystem management when rigorous ecological data are lacking. We define the effectiveness of the wetland management strategy by its ability to maintain sustainable minimum water levels that are required to support ecological processes. These minimum water requirements are defined in water management and environmental policy of the wetland. Here, we trial the method on Forrestdale Lake, a wetland in a region experiencing a markedly drying climate. ATPs were defined by linking key ecological objectives identified by policy documents to threshold values for water depth. We then used long-term hydrologic data (1978–2012) to assess if and when thresholds were breached. We found that from the mid-1990s, declining wetland water depth breached ATPs for the majority of the wetland objectives. We conclude that the wetland management strategy has been ineffective from the mid-1990s, when the region’s climate dried markedly. The extent of legislation, policies, and management authorities across different scales and levels of governance need to be understood to adapt ecosystem management strategies. Empirical verification of the ATP assessment is required to validate the suitability of the method. However, in general we consider ATPs to be a useful desktop method to assess the suitability of management when rigorous ecological data are lacking.

Water depth and lake-wide water level fluctuation influence on α- and β-diversity of coastal wetland fish communities

Abstract Coastal wetlands in the Laurentian Great Lakes are critical habitats for supporting fish diversity and abundance within the basin. Insight into the coupling of biodiversity patterns with habitat conditions may elucidate mechanisms shaping diverse communities. Within coastal wetlands, water depth as well as fluctuations in lake-wide water levels over inter-annual timescales, both have the potential to influence fish communities. Water level fluctuation can influence fish habitat structure (e.g., vegetation) in Great Lakes coastal wetlands, but it is unclear how water depth and lake-wide water level fluctuations affect fish community composition and diversity. Using β dissimilarity indices and multivariate ordination techniques, we assessed fish community structure among bulrush (Schoenoplectus acutus)-dominated wetlands in Saginaw Bay, Lake Huron, USA. We examined whether community structure was related to wetland water depth at the time of sampling and whether fish communities were more similar among years with similar Lake Huron water levels. Results suggested relatively high levels of both spatial (among wetlands) and temporal (among year) community dissimilarity that was driven primarily by species turnover. Thus, variability in water depths among wetlands and in Lake Huron water levels among years likely both contribute to regional fish diversity. Further, fish abundance and alpha diversity were positively correlated with wetland water depth at the time of sampling. Both climate change and anthropogenic water level stabilization may alter the magnitude and timing of water level fluctuations in the Great Lakes. Our data suggest that these changes could affect local fish community composition and regional fish diversity.

Nitrogen Dynamics in Two Created Riparian Wetlands over Space and Time

AbstractTemporal and spatial variations of nitrogen (N) soil storages and fluxes were examined at two 1-ha created riverine wetlands in the U.S. Midwest. Soil N content (total N, organic-N, NO3-N, and NH4-N), N accumulation rates, and soil C:N ratios were compared between the two wetlands constructed 15 years earlier (one was planted and the other left to naturally colonize). Differences in wetland soil N content and accumulation were also examined in relation to proximity of river input and relative to a range of topographic features related to wetland water depth. The planted and naturally colonized wetlands showed similar rates of N accumulation. However, differences were detected related to the content of mineralized forms of N (NO3-N and NH4-N) that may relate to the history of vegetation communities at these wetlands. Significant spatial variation of N accumulation was detected within the wetlands, with the highest rates found in the deeper open water communities compared to shallow emergent marsh/e...

Physiological condition of juvenile wading birds in relation to multiple landscape stressors in the Florida Everglades: effects of hydrology, prey availability, and mercury bioaccumulation.

The physiological condition of juvenile birds can be influenced by multiple ecological stressors, and few studies have concurrently considered the effects of environmental contaminants in combination with ecological attributes that can influence foraging conditions and prey availability. Using three temporally distinct indices of physiological condition, we compared the physiological response of nestling great egrets (Ardea alba) and white ibises (Eudocimus albus) to changing prey availability, hydrology (water depth, recession rate), and mercury exposure in the Florida Everglades. We found that the physiological response of chicks varied between species and among environmental variables. Chick body condition (short-term index) and fecal corticosterone levels (medium-term) were influenced by wetland water depth, prey availability, region, and age, but not by mercury contamination. However, mercury exposure did influence heat shock protein 70 (HSP70) in egret chicks, indicating a longer-term physiological response to contamination. Our results indicate that the physiological condition of egret and ibis chicks were influenced by several environmental stressors, and the time frame of the effect may depend on the specialized foraging behavior of the adults provisioning the chicks.

Adaptive wetland management in an uncertain and changing arid environment

Wetlands in the arid western United States provide rare and critical migratory bird habitat and constitute a critical nexus within larger social-ecological systems (SES) where multiple changing land-use and water-use patterns meet. The Bear River Migratory Bird Refuge in Utah, USA, presents a case study of the ways that wetland managers have created adaptive management strategies that are responsive to the social and hydrological conditions of the agriculture-dominated SES within which they are located. Managers have acquired water rights and constructed infrastructure while cultivating collaborative relationships with other water users to increase the adaptive capacity of the region and decrease conflict. Historically, water management involved diversion and impoundment of water within wetland units timed around patterns of agricultural water needs. In the last 20 years, managers have learned from flood and drought events and developed a long-term adaptive management plan that specifies alternative management actions managers can choose each year based on habitat needs and projected water supply. Each alternative includes habitat goals and target wetland water depth. However, wetland management adapted to agricultural return-flow availability may prove insufficient as population growth and climate change alter patterns of land and water use. Future management will likely depend more on negotiation, collaboration, and learning from social developments within the SES than strictly focusing on water management within refuge boundaries. To face this problem, managers have worked to be included in negotiations with regional water users, a strategy that may prove instructive for other wetland managers in agriculture-dominated watersheds.

Modeling flow in wetlands and underlying aquifers using a discharge potential formulation

Summary An accurate assessment of water and nutrient balances in large scale wetland systems such as the Florida Everglades requires conjunctive modeling of surface water flow in wetlands and groundwater flow in underlying aquifers. Earlier work was based on the finite difference code MODFLOW with a special “wetlands package.” This model treats the wetland flow as laminar with a very high transmissivity that is proportional to the wetland water depth cubed. However, these MODFLOW solutions appear sensitive to this highly non-linear wetland transmissivity, particularly under conditions of low vegetation density when the model may fail to converge. We propose to formulate the governing differential equation in terms of a discharge potential instead of potentiometric heads as done in MODFLOW, but otherwise using the same assumptions as in its wetlands package. We tested our approach on a few cases of one- and two-dimensional flow, both with a constant and a varying wetland bottom elevation. For the latter the discharge potential represents an irrotational part of the flow field which is combined with a component of the flow field that contains the curl. We found that both the robustness and the accuracy of the solution in terms of potentials was superior to the solution in terms of heads. In some cases the latter solution failed altogether, even for simple one-dimensional flow. We applied our method to model the effects of wetland hydrology on the nutrient redistribution in and near tree islands. We found that the subtle velocity distributions near these tree islands, as resulted from our conjunctive wetlands and groundwater flow solution, could help explain the increased nutrient depositions at these islands, particularly at the head of the islands, where, consequently, most of the vegetation occurs.

Effects of local and landscape-scale habitat variables on abundance and reproductive success of wetland birds

Both local and landscape-scale habitat variables influence the abundance of wetland breeding birds. Few studies, however, simultaneously assess the effects of habitat variables at multiple spatial scales or consider effects on reproductive success. Therefore, we examined the effects of wetland and landscape-scale habitat variables on the abundance of nine breeding bird species and the effects of nest, wetland, or landscape-scale habitat variables on the nest success, clutch size, or number of fledglings of four species at 15 cattail (Typha sp.)-dominated wetlands in an agricultural region around Peterborough, Ontario, Canada. The abundance of Least Bittern (Ixobrychus exilis), Common Moorhen (Gallinula chloropus), and Marsh Wren (Cistothorus palustris) increased as wetland water depth increased; the abundance of Common Moorhen and Marsh Wren increased as wetland size increased; and the abundance of Marsh Wren increased as the amount of wetland in the surrounding landscape increased. Red-winged Blackbird (Agelaius phoeniceus) nest success decreased as nest cover increased. Clutch sizes were uninfluenced by the habitat variables that we considered. The number of Red-winged Blackbird fledglings per successful nest increased as wetland size increased and as the amount of wetland in the surrounding landscape increased. We speculate that food limitation in small wetlands may be responsible for the pattern in Red-winged Blackbird fledging success. The abundance and nest success of Virginia Rail (Rallus limicola) and Sora (Porzana carolina) were uninfluenced by the habitat variables we considered. Future research should consider mate attraction and productivity in relation to local and landscape-scale habitat variables for these and other secretive species. Our study suggests that wetland conservation will be most effective if it considers habitat variables at multiple spatial scales.

Simplified Volume-Area-Depth Method for Estimating Water Storage of Prairie Potholes

The Prairie Pothole Region (PPR) of North American contains millions of wetlands that provide important hydrological and ecological functions. Modeling these processes relies on relationships that relate wetland water depth to volume. Methods suitable for investigating water storage in regularly shaped wetlands have already been developed when two coefficients are known. We tested the robustness of the full and simplified volume (V) area (A) depth (h) methods to accurately estimate volume for the range of wetland shapes occurring across the PPR. The full V-A-h method was found to accurately estimate volume (errors ≤5%) across wetlands of various shapes, and is therefore suitable for calculating water storage in the variety of wetland shapes found in the PPR. Analysis of the simplified V-A-h method showed that <10% volume error can be achieved with concurrent measures of surface area and depth in the spring when water levels are ∼70% of hmax, and also in late summer prior to water levels dropping below 10 cm. Applying the simplified V-A-h method according to the guidelines presented herein will allow for accurate, time effective water storage estimates for multiple wetlands, thereby allowing hydrological and ecological functions to be modeled.

Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater

Constructed wetland treatment of swine wastewater probably involves substantial denitrification. Our objective was to assess denitrification and denitrification enzyme activity (DEA) in such wetlands in relation to plant communities, N loading, carbon or nitrogen limitations, and water depth. Two wetland cells each 3.6 m wide and 33.5 m long were connected in series. One set of cells was planted with rushes and bulrushes, including soft rush (Juncus effusus L.), softstem bulrush [Schoenoplectus tabernaemontani (K.C. Gmel.) Pallal, American bulrush [Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller], and woolgrass bulrush [Scirpus cyperinus (L.) Kunth]. Another set was planted with bur-reeds and cattails, including American bur-reed (Sparganium americanum Nutt.), broadleaf cattail (Typha latifolia L.), and narrowleaf cattail (Typha angustifolia L.). The sets will be referred to herein as bulrush and cattail wetlands, respectively. Denitrification and DEA were measured via the acetylene inhibition method in intact soil cores and disturbed soil samples that were taken during four years (1994-1997). Although DEA in the disturbed samples was greater than denitrification in the core samples, the measurements were highly correlated (r2 > or = 0.82). The DEA was greater in the bulrush wetlands than the cattail wetlands, 0.516 and 0.210 mg N kg(-1) soil h(-1), respectively; and it increased with the cumulative applied N. The DEA mean was equivalent to 9.55 kg N ha(-1) d(-1) in the bulrush wetlands. We hypothesized and confirmed that DEA was generally limited by nitrate rather than carbon. Moreover, we determined that one of the most influential factors in DEA was wetland water depth. In bulrush wetlands, the slope and r2 values of the control treatment were -0.013 mg N kg(-1) soil h(-1) mm(-1) depth and r2 = 0.89, respectively. Results of this investigation indicate that DEA can be very significant in constructed wetlands used to treat swine wastewater.