Riparian Wetland Area Research Articles

Shifts in soil phosphorus fractions during seasonal transitions in a riparian floodplain wetland

Losses of phosphorus from soil to surface waters in agricultural areas have been linked to substantial declines in water quality. Riparian wetlands can potentially intercept phosphorus mobilized from upland soils before it reaches connecting waterways, but the capacity of wetlands to buffer against downstream losses of P is poorly understood, especially in northern temperate zones. In these regions, the spring freshet releases large volumes of water from snowmelt and soil pore water during the time when microbial productivity, which transfers available P into biomass, is low. In addition, losses of P in runoff may be exacerbated by freeze-thaw cycling (FTC) in soil during late winter and early spring through the physical degradation of organic matter. We investigated P dynamics from late fall through spring thaw and into summer to assess P transfers between inorganic, organic and microbial biomass pools, as functions of season and distance from a river. The site is located on the Grand River in southern Ontario, which discharges to Lake Erie, and consists of riparian wetland and wooded areas. Reactive P (Olsen P) and microbial biomass P (PMBIO) increased with distance from the river and varied more over time in the wetland soil compared to the adjacent wooded area, reflecting higher variability in vegetation, topography and hydrology. The positive correlation between microbial biomass P and microbes linked to ammonification supports the release of N and P through mineralization pathways as spring progresses, with microbial biomass decreasing in June as plant growth increases. There was evidence for leaching of Fe and Al, and lower concentrations of total P, in the transect proximate to the river. Seasonal flooding during spring thaw contributed to a pulse of dissolved reactive P, but temperature monitoring showed that the wetland soil did not experience freeze-thaw cycling. Investigation of FTC using wetland soil in mesocosms indicated that multiple FTC (>3) were necessary to increase the pool of reactive soil P, with the highest amount of soil reactive P observed after six FTC, when dissolved reactive P also tended to increase.

Methane emission is independent from silicon availability in warm-temperate Chamaecyparis obtusa forest soils from diverse topographic positions

It has been recently reported that silicon (Si) increases methane (CH4) emission from peats through mobilizing phosphorus and organic carbon bound to iron minerals and stimulating microbial activities. However, it is unknown whether this effect of Si applies in other environments, such as warm temperate forest soils that function primarily as a CH4 sink but occasionally as a CH4 source. We tested our hypothesis that CH4 emission should increase with Si availability in warm temperate forest soils under anaerobic conditions, by incubating four soil samples collected from a variety of topographic positions in the Kiryu Experimental Watershed, in Shiga, Japan. The soil characteristics including soil pH and total phosphorus and iron contents varied among the soils. Much greater CH4 emission was observed in the soils from the riparian wetland areas than in those from the upland areas. The onset of methanogenesis was not accelerated by Si addition during the incubation. At the end of the incubation, the Si addition did not increase total CH4 production from the soils. A lack of the Si effects would be due to low quantities of phosphorus retained by iron minerals in the entire area of this watershed and high abundance of more potent electron acceptors in the upland. Overall, our results suggest that increasing Si availability exerts little influence on CH4 emissions from warm temperate forest soils under the used experimental conditions in this watershed.

Dam Effects on Downstream Riparian Wetlands: The Nenjiang River, Northeast China

Many studies have found that damming a river can change downstream hydrology, sediment transport, channel morphology, and fish habitat. However, little is known about river dam effects on downstream riparian wetland dynamics and their quantitative relationship with hydrological alterations. In this study, hydrological time series and wetland distribution data spanning nearly 40 years (1978–2016) before and after the construction of a large dam in 2005 across the Nenjiang River in Northeast China were used to reveal the impact of dam on the downstream discharge regime and wetland degradation. Hydro-statistical and stepwise multiple regression analyses were performed to quantify the relationship of riparian wetland area with a metrics of 33 hydrological indicators. Dam construction caused decline in peak discharge, flood frequency, and magnitude. Moreover, 150 km riparian wetlands along the downstream of the dam was largely reduced. The count and duration of high flow pulses, 1-day maximum, and date of maximum discharge changed significantly after the dam construction. The hydrological changes have made a significant contribution to the 44% reduction in riparian wetlands following the dam construction. Our results indicated that hydrological alterations caused by dam regulation led to the area reduction of downstream riparian wetlands. The findings provide relevant information for developing best dam operation practices to protect and restore downstream wetland ecosystems.

Impact of dam on inundation regime of flood plain wetland of punarbhaba river basin of barind tract of Indo-Bangladesh

Present study raises a serious issue of wetland loss and transformation due to damming and water diversion. At present study, it is noticed that overall rainfall trend (−0.006) of the study period (1978–2015) remains unchanged but riparian wetland area is attenuated after damming both pre monsoon (March to May) and post monsoon season (October to December). Total wetland area in pre- and post- monsoon seasons is respectively reduced from 42.2km2 to 27.87km2, and from 277.85km2 to 220.90km2 in post dam period. Transformation of frequently inundated wetland area into sparsely inundated wetland is mainly triggered by flow modification due to installation of Komardanga dam and Barrage over Punarbhaba and its major tributary Tangon river. Sparsely inundated seasonal wetland area is rapidly reclaimed for agricultural practice. This extreme issue will invite instability in socio-ecological setup of the neighbouring region.

What we can learn from a wetland water balance? Narew National Park case study

Analyses carried out in this paper aimed to provide an integrated, dynamic, yet simple water balance model for riparian wetland areas with insufficient observation data. The proposed approach was based on a combination of a conceptual model of wetland water balance with an integrated river basin model SWAT (Soil and Water Assessment Tool). It allowed determining the water balance components of the protected part of the Upper Narew River valley. Scenario analyses were conducted with the aim of evaluating the effect of changes in external and internal factors on the water storage within the NNP wetlands, with a particular emphasis on the issue of soil desiccation. The model calibration was based on comparing simulated water storage within the wetland with the mean groundwater depths for the period 2000–2004. The reference conditions were defined by the “Baseline” scenario (water balance simulations for the period 1990–2009), whereas future conditions were represented by three scenarios: “Climate” (climatic changes according to two GCMs driven by SRES A2 emission scenarios), “Reservoir” (changes in operation of Siemianówka reservoir situated upstream of the study area) and “Succession” (changes in vegetation cover of the NNP). The results allowed identifying possible factors contributing to degradation of hydrogenic habitats. The conclusion from this study is that the largest impact on the water storage within the NNP wetland, and thus on water conditions for hydrogenic habitats can be expected under projected climate change, whereas scenarios of change in reservoir operation and vegetation succession have a rather moderate impact.

Natural and Anthropogenic Causes of Vegetation Changes in Riparian Wetlands Along the Lower Reaches of the Yellow River, China

There are many natural and anthropogenic impacts on the vegetation in riparian wetlands. The Yellow River in the North of China is one of the biggest rivers of the world, but the riparian wetland area is very small. The monitoring of these wetlands has increased in the last years because of the high ecological importance and increasing pressure due to economic development and increasing use of water resources. We use remote sensing and hydrologic data to analyze the change of wetland vegetation in the Zhengzhou natural reserve, which is affected by a rapid population growth and change of water flow. The main findings are: (1) the vegetation cover of the study area decreased from 1984 to 2011, (2) the hydrologic boundary conditions changed dramatically after the construction of a dam upstream and floods have almost disappeared under the new water resource management, (3) there is a conflict between the protection of the wetland vegetation and its use for recreation and tourism. Actually, anthropogenic factors are the main reasons for wetland degradation, and the government and the water management department should pay more attention to the protection of the remaining wetlands and the environmental balance.

Variability of water quality in a riparian wetland with interacting shallow groundwater and surface water

AbstractLowland catchment hydrology is dominated by shallow groundwater with complex interactions between groundwater and surface water. In lowland catchments of N Germany, a high fraction of agricultural land is drained and therefore influenced by fast water transport to discharge systems with resulting alterations to water quality. The investigated catchment area “Kielstau” (approx. 50 km2) in the N of Schleswig‐Holstein serves as an example. Detailed investigations on the interactions between groundwater, river, and ditch‐water quality were evaluated at a drained riparian wetland area (0.15 km2) used as grassland in the central part of this catchment. The water quality in the drainage ditches showed variability dependent on their hydrological integration. At the far‐from‐river end, groundwater and ditch‐water quality were in most parameters much more alike than at the close‐to‐river end. The composition of ditch water at the close‐to‐river end of the ditch was determined by transformation processes and dilution which took place along the ditch much more than exfiltration processes like those that were dominant at the far‐from‐river end. In most cases, the mean NH$ _4^+ $ concentrations were higher in the groundwater than in the ditches, but the highest concentrations were found all along the time in the close‐to‐river sampling points and in the river. The highest NO$ _3^- $ concentration was observed in a ditch influenced by an adjacent arable field as well as in the river. The concentrations of phosphate and total P were lower in groundwater than in the ditch water.

Riparian wetlands for enhancing the self-purification capacity of streams

Best Management Practices (BMPs) are increasingly used to restore river water quality but design guidance is limited. An alternative approach to remediating diffuse pollution loads is to identify the most polluting high flows from pollutographs and hydrographs and spill these flows into riparian treatment wetlands for treatment before drainage back into the watercourse. The approach is demonstrated for two contrasting catchments in Scotland impacted by diffuse pollution. The Caw Burn receives industrial estate drainage with high suspended solids, hydrocarbons, BOD and ammoniacal-nitrogen concentrations. Applying the proposed design criteria demonstrated that the existing retrofit BMP system at the site is undersized (4950 m2) compared to the required wetland area (11,800 m2), but accommodating the additional area is likely to be expensive. The second case-study is Brighouse Bay where bathing waters are impacted by faecal indicator organisms derived primarily from livestock runoff. In this catchment the riparian wetland area required to retain runoff so that E. coli bacteria would die-off to concentrations below bathing water standards was estimated to be 3-6ha (0.5-1% of catchment area). Further refinement and testing of the design approach is required, including consideration of other factors such as vegetation type, ownership and maintenance, to develop a more holistic approach to river restoration.

Soil–landscape relationships at the lower reaches of a watershed at Bear Creek near Oak Ridge, Tennessee

The watersheds at Bear Creek, Oak Ridge, TN, have similar soil–landscape relationships. The lower reaches of many of these watersheds consist of headwater riparian wetlands situated between sloping non-wetland upland zones. The objectives of this study are to examine the effects of (i) slope and geomorphic processes, (ii) human impacts, and (iii) particular characteristics of soils and saprolite that may effect drainage and water movement in the wetlands and adjacent landscapes in one of these watersheds. A transect was run from west to east in a hydrological monitored area at the lower reaches of a watershed on Bear Creek. This transect extended from a steep side slope position across a floodplain, a terrace, and a shoulder slope. On the upland positions of the Nolichucky Shale, mass wasting, overland flow and soil creep currently inhibit soil formation on the steep side slope position where a Typic Dystrudept is present, while soil stability on the shoulder slope has resulted in the formation of a well-developed Typic Hapludult. In these soils, argillic horizons occur above C horizons on less sloping gradients in comparison to steeper slopes, which have Bw horizons over Cr (saprolite) material. A riparian wetland area occupies the floodplain section, where a Typic Endoaquept is characterized by poorly drained conditions that led to the development of redoximorphic features (mottling), gleying, organic matter accumulation, and minimal development of subsurface horizons. A thin colluvial deposit overlies a thick well developed Aquic Hapludalf that formed in alluvial sediments on the terrace position. The colluvial deposit from the adjacent shoulder slope is thought to result from soil creep and anthropogenic erosion caused by past cultivation practices. Runoff from the adjacent sloping landscape and groundwater from the adjacent wetland area perhaps contribute to the somewhat poorly drained conditions of this profile. Perched watertables occur in upland positions due to dense saprolite and clay plugging in the shallow zones of the saprolite. However, no redoximorphic features are observed in the soil on the side slope due to high runoff. Remnants of the underlying shale saprolite, which occur as small discolored zones resembling mottles, are also present. The soils in the study have a CEC of <10 cmol kg −1, silt loam textures and Fe d values of 0.5–4.3%. These soils are also mainly acidic and low in total carbon.

Longitudinal and seasonal patterns of stream acidity in a headwater catchment on the Appalachian Plateau, West Virginia, U.S.A.

The chemical composition during baseflow was used to elucidate the fundamental processes controlling longitudinal and seasonal patterns of stream acidity in Yellow Creek, a chronically acidic headwater (pH range 3.7--4.2) on the Appalachian Plateau in northeastern West Virginia. Sulfate concentrations controlled the variability of stream acidity within the Yellow Creek catchment. Decreases in stream free H+ acidity with decreasing elevation likely resulted from SO 4 2− retention in riparian wetland areas as well as spatial variation in dominant tree species. Seasonal variations in free H+ and inorganic monomeric aluminum (Aln+) concentrations appeared related to seasonal fluctuations in baseflow discharge which was controlled by vegetative activity. Baseflow stream discharge, as well as H+ and Aln+ acidity, gradually declined during the growing season (June through October), likely reflecting microbial SO 4 2− > reduction in saturated anaerobic environments within riparian wetlands. A marked pulse of stream H+, Aln+, and SO 4 2− coincided with an abrupt increase in baseflow discharge resulting from the cessation of transpiration after leaf-fall in November. This seasonal pattern suggests that autumn may be a critical period for eastern brook trout in streams draining wetlands on the Appalachian Plateau.

Contamination of riparian wetlands from past copper mining and smelting in the headwaters region of the Clark Fork River, Montana, U.S.A.

The headwaters region of the Chark Fork River in western Montana. U.S.A., has been the center of copper mining and smelting activities for approximately 120 years. Poor control of waste materials led to widespread contamination. High metal concentrations have been found in bed sediments of the river 381 km downstream and in reservoir sediments 500 km downstream. Fish and aquatic insects have been influenced by metal contamination, but little has been published about metal influences on riparian wetland areas, either sediments or plant species. In this study sediment and a dominant emergent macrophyte species ( Typha latifolia) were sampled from eight small riparian wetlands along the upper 190 km of the Clark Fork and from one site on an uncontaminated tributary to the Clark Fork River. Elevated concentrations of copper, zinc. and frequently, lead were found in plant tissues and sediments of 8 Clark Fork sites compared to the local reference site. Total and HCI-extractable copper and zinc concentrations in unsieved and sieved (<60 micron) sediment were strong and highly significant predictors of the metal concentrations in Typha latifolia root tissues.

Interactions between groundwater and surface water in a virginia coastal plain watershed. 1. Hydrological flowpaths

AbstractA field study of surface water and groundwater interactions during baseflow and stormflow conditions was performed at the Reedy Creek watershed in the Virginia Coastal Plain. Three estimates of the average saturated hydraulic conductivity (Ks) of the unconfined aquifer were in reasonable agreement (ranging from 0.0033 to 0.010 cm/s), indicating that baseflow in the creek is entirely from the drainage of shallow groundwater from the relatively thin (1–6 m thick) unconfined aquifer. This relatively permeable surficial aquifer was found to be underlain by dark, olive grey, clay‐silt and diatomaceous Miocene deposits of low permeability known as the Calvert Formation, which is believed to function as a confining bed in the area.A chemical hydrograph separation technique was used to resolve the contributions of [old] (pre‐event) and [new] (event) water to stormflow. Results from a major rainstorm indicated that old water dominated the stormflow response of the watershed, although the new water contribution approached 40% at the hydrograph peak. Stormflow at Reedy Creek appears to result from saturation overland flow from variable source areas which include the stream channels and a significant part of the riparian wetland area. This response appears to be attributable to the transient dynamics of the shallow groundwater flow system and to the formation of localized groundwater mounds which raise the water‐table to the wetland surface.

Forest sources and pathways of organic matter transport to a blackwater stream: a hydrologic approach

Quantitative information regarding landscape sources and pathways of organic matter transport to streams is important for assessing impacts of terrestrial processes on aquatic ecosystems. We quantified organic C, a measure of organic matter, flowing from a blackwater stream draining a 12.6 km2 watershed on the upper Atlantic Coastal Plain in South Carolina, and utilized a hydrologic approach to partition this outflow between its various pathways from upland and wetland forest sources. Results of this study indicate that 28.9 tonnes C yr−1 were exported in stream flow, which was estimated to be 0.5% of the annual C input from forest detritus to the watershed. Upland forest, which covers 94% of the watershed area, contributed only 2.0 tonnes C yr−1 to stream flow, which amounted to 0.04% of detritus annually produced by the upland forest. Organic matter was transported from uplands to the stream almost entirely through groundwater. Apparently, upland soils are too sandy to support overland flow, and the sloping topography insufficiently extensive or steep enough to drive important quantities of interflow. Riparian wetland forest, which covers only 6% of the watershed area, contributed 26.9 tonnes C yr−1 to stream flow, amounting to about 10.2% of detritus annually produced by the wetland forest. Dissolved organic C leached from wetland soil accounted for 63% of all organic C entering the stream, and was transported chiefly in baseflow. These results indicate that upland detritus sources are effectively decoupled from the stream despite the sandy soils and quantitatively confirm that even small riparian wetland areas can have a dominant effect on the overall organic matter budget of a blackwater stream. In view of the recognized importance of dissolved organic matter in facilitating transport of other substances (e.g., cation nutrients, metals, and insoluble organic compounds), our results suggest that the potential for movement of these substances through wetland soils to streams in this region is high.

Determination of contributing areas for saturation overland flow from chemical hydrograph separations

A recurring problem in watershed hydrology is the identification of flow paths along which water is routed in both surface and subsurface environments. In particular, the question of whether storm flow is composed primarily of water flowing over the land surface (overland flow) or beneath the land surface (subsurface flow) is significant, because the former flow path provides for little soil contact, while the latter allows for extensive interaction with subsurface materials. The Reedy Creek watershed (45.1 km2) in the Virginia Coastal Plain has been the subject of field hydrogeological, hydrochemical, and hydrological studies since 1989. Results from chemical separation of six storm flow hydrographs indicate that saturation overland flow (including both direct precipitation onto and return flow to the surface) from saturated contributing areas is the dominant storm flow generation mechanism in the watershed; new water composed 11–38% of creek discharge at the hydrograph peaks, and maximum 24‐hour rainfall intensity explained 96% of the total variation in the peak new water contribution among the six events. Estimates of new water‐contributing areas determined from the chemical separations were found to vary as a function of antecedent conditions and were also found to be consistent with estimates of areas of likely surface saturation (e.g., perennial channels, open water, and riparian wetland areas) based on field observations and topographic maps.

Wetland and aquatic habitats

Riparian wetland areas often represent critical corridors for animal and plant dispersion in wildland watersheds and downstream river systems. It is essential that integrated management of riparian wetland areas be developed to reverse the loss of biological diversity. Agricultural and urban uses, and related water developments, have led to a marked decline of stream-side wetland habitats. Six major ways are discussed in which conventional agriculture alters wetlands and aquatic habitats: wetland drainage, water diversions, stream channelization, bank stabilization, grazing, and the release of agricultural pollutants. This article discusses these practices and suggests ways biological diversity can be protected, or even enhanced. In addition, aquaculture is discussed as a new force which affects the diversity of aquatic organisms. Aquaculture methods range in intensity of management from low to high. The higher the intensity the potentially more disruptive practices can be to surrounding aquatic systems. Management for biological diversity as well as for food production should be encouraged.

Use of avian and mammalian guilds as indicators of cumulative impacts in riparian-wetland areas

A new method of assessing cumulative effects of human activities on bird and mammal communities of riparian-wetland areas was developed by using response guilds to reflect how species theoretically respond to habitat disturbance on a landscape level. All bird and mammal species of Pennsylvania were assigned values for each response guild using documented information for each species, to reflect their sensitivity to disturbances; high guild scores corresponded to low tolerance toward habitat disturbance. We hypothesized that, given limited time and resources, determining how wildife communities change in response to environmental impacts can be done more efficiently with a response-guild approach than a single-species approach. To test the model, censuses of birds and mammals were conducted along wetland and riparian areas of a protected and a disturbed watershed in central Pennsylvania. The percent of bird species with high response-guild scores (i.e., species that had specific habitat requirements and/or were neotropical migrants) remained relatively stable through the protected watershed. As intensity of habitat alteration increased through the disturbed watershed, percentage of bird species with high response-guild scores decreased. Only 2%–3% of the neotropical migrants that had specific habitat requirements were breeding residents in disturbed habitats as compared to 17%–20% in reference areas. Species in the edge and exotic guild classifications (low guild scores) were found in greater percentages in the disturbed watershed. Composition of mammalian guilds showed no consistent pattern associated with habitat disturbance. Avian response guilds reflected habitat disturbance more predictively than mammalian response guilds.