Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Hydrology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
USGS1995

Hydrological and thermal response of lakes to climate: Description and modeling

Lake systems continually respond to climatic conditions that vary over broad scales of space and time. The spatial distribution of lakes on the Earth’s surface is indicative of long-term patterns of atmospheric circulation, and the annual cycle of climate over lake basins is reflected in seasonal change in the size and temperature of lakes. Lake size is determined by the balance of water inputs and outputs, and lake temperature is governed by the balance of heat inputs and outputs. The lake hydrological and energy balances are coupled to the atmosphere. In response to the inputs of mass, energy, and momentum (precipitation, radiation, and wind stress), lakes return heat and moisture to the atmosphere through conduction and evaporation. Global, regional, or local change in the hydrological or thermal states of lakes thus represent interactive responses to climatic variation in the supply of water and energy.

Book chapter↗
USGS1989

Interrelationships among hydrologic-budget components of a northern Wisconsin seepage lake and implications for acid-deposition modeling

Components of the hydrologic budget for a northern Wisconsin seepage lake were analyzed by applying correlation and regression techniques to monthly data. Analyses for the 1981–83 water years revealed a statistically significant, direct relationship between storage change and precipitation-evaporation balance. Ground-water outflow was negatively correlated with ground-water inflow, and this relationship was influenced by similar relationships for both hydraulic gradients and cross-sectional areas in outflow versus inflow regions of the lake. Neither ground-water outflow nor inflow was significantly related to precipitation, evaporation, storage change, or lake stage; this may reflect a lag in response time of the ground-water system compared to the lake. The results (1) emphasize the complexity of factors that influence ground-water interactions with seepage lakes and (2) suggest the importance of completing detailed hydrologic studies of these systems before mechanistic models, such as those developed to predict effects of acid deposition, are applied.

Wisconsin↗
USGS1997

Hydrologic indices for nontidal wetlands

Two sets of hydrologic indices were developed to characterize the water-budget components of nontidal wetlands. The first set consisted of six water-budget indices for input and output variables, and the second set consisted of two hydrologic interaction indices derived from the water-budget indices. The indices then were applied to 19 wetlands with previously published water-budget data. Two trilinear diagrams for each wetland were constructed, one for the three input indices and another for the three output indices. These two trilinear diagrams then were combined with a central quadrangle to form a Piper-type diagram, with data points from the trilinear diagrams projected onto the quadrangle. The quadrangle then was divided into nine fields that summarized the water-budget information. Two quantitative "interaction indices" were calculated from two of the six water-budget indices (precipitation and evapotranspiration). They also were obtained graphically from the water-budget indices, which were first projected to the central quadrangle of a Piper-type diagram from the flanking trilinear plots. The first interaction index (l) defines the strength of interaction between a wetland and the surrounding ground- and surface-water system. The second interaction index (S) defines the nature of the interaction between the wetland and the surrounding ground- and surface-water system (source versus sink). Evaluation of these indices using published wetland water-budget data illustrates the usefulness of the technique.

Wetlands↗
USGS1989

Hydrologic and water-quality characteristics of a Wetland receiving wastewater effluent in St. Joseph, Minnesota

Hydrologic and water-quality characteristics were determined for a wetland being used for tertiary treatment of wastewater in St. Joseph, Minnesota. The wetland consists of spruce-tamarack fen and a cattail marsh, with the wastewater being discharged into the fen, and the fen draining into the marsh. The wetland is underlain by flat-lying glacial outwash that ranges from 0 to greater than 20 m in thickness. Horizontal ground-water movement in the outwash aquifer is toward the wetland from the south, east, and west. There is a strong upward vertical hydraulic gradient (about 0.1) in the ground-water flow system beneath and around the wetland. Regionally, the glacial-outwash aquifer is unconfined, but it is confined or partly confined locally by peat deposits under the wetland. Analysis of the hydrologic balance of the fen from October 1985 through September 1986 indicates that the inflow was 44 percent ground water, 38 percent wastewater, 11 percent runoff (storm sewer), and 7 percent precipitation. The fen outflow was 93 percent surface water and 7 percent evapotranspiration. Inflow to the marsh was 74 percent surface water, 21 percent ground water, and 5 percent precipitation. Outflow from the marsh was 94 percent surface water and 6 percent evapotranspiration. Wastewater contributed 74,996, and 81 percent of the total suspended solids, total phosphorus, and total ammonia plus organic nitrogen in the fen, respectively. Other chemical inputs were from the storm sewer, ground water, and atmospheric deposition. The fen was found to retain 34, 14, and 14 percent of the suspended solids, total phosphorus, and total ammonia plus organic nitrogen, respectively. The marsh retained 44, 18, and 22 percent of these three constituents, respectively.

Minnesota↗
USGS2015

A framework for effective use of hydroclimate models in climate-change adaptation planning for managed habitats with limited hydrologic response data

Climate-change adaptation planning for managed wetlands is challenging under uncertain futures when the impact of historic climate variability on wetland response is unquantified. We assessed vulnerability of Modoc National Wildlife Refuge (MNWR) through use of the Basin Characterization Model (BCM) landscape hydrology model, and six global climate models, representing projected wetter and drier conditions. We further developed a conceptual model that provides greater value for water managers by incorporating the BCM outputs into a conceptual framework that links modeled parameters to refuge management outcomes. This framework was used to identify landscape hydrology parameters that reflect refuge sensitivity to changes in (1) climatic water deficit (CWD) and recharge, and (2) the magnitude, timing, and frequency of water inputs. BCM outputs were developed for 1981–2100 to assess changes and forecast the probability of experiencing wet and dry water year types that have historically resulted in challenging conditions for refuge habitat management. We used a Yule’s Q skill score to estimate the probability of modeled discharge that best represents historic water year types. CWD increased in all models across 72.3–100 % of the water supply basin by 2100. Earlier timing in discharge, greater cool season discharge, and lesser irrigation season water supply were predicted by most models. Under the worst-case scenario, moderately dry years increased from 10–20 to 40–60 % by 2100. MNWR could adapt by storing additional water during the cool season for later use and prioritizing irrigation of habitats during dry years.

California↗
USGS2011

The effects of permafrost thaw on soil hydrologic, thermal, and carbon dynamics in an Alaskan peatland

Recent warming at high-latitudes has accelerated permafrost thaw in northern peatlands, and thaw can have profound effects on local hydrology and ecosystem carbon balance. To assess the impact of permafrost thaw on soil organic carbon (OC) dynamics, we measured soil hydrologic and thermal dynamics and soil OC stocks across a collapse-scar bog chronosequence in interior Alaska. We observed dramatic changes in the distribution of soil water associated with thawing of ice-rich frozen peat. The impoundment of warm water in collapse-scar bogs initiated talik formation and the lateral expansion of bogs over time. On average, Permafrost Plateaus stored 137 ± 37 kg C m -2 , whereas OC storage in Young Bogs and Old Bogs averaged 84 ± 13 kg C m -2 . Based on our reconstructions, the accumulation of OC in near-surface bog peat continued for nearly 1,000 years following permafrost thaw, at which point accumulation rates slowed. Rapid decomposition of thawed forest peat reduced deep OC stocks by nearly half during the first 100 years following thaw. Using a simple mass-balance model, we show that accumulation rates at the bog surface were not sufficient to balance deep OC losses, resulting in a net loss of OC from the entire peat column. An uncertainty analysis also revealed that the magnitude and timing of soil OC loss from thawed forest peat depends substantially on variation in OC input rates to bog peat and variation in decay constants for shallow and deep OC stocks. These findings suggest that permafrost thaw and the subsequent release of OC from thawed peat will likely reduce the strength of northern permafrost-affected peatlands as a carbon dioxide sink, and consequently, will likely accelerate rates of atmospheric warming.

Alaska↗
USGS2023

Postfire hydrologic response along the central California (USA) coast: Insights for the emergency assessment of postfire debris-flow hazards

The steep, tectonically active terrain along the Central California (USA) coast is well known to produce deadly and destructive debris flows. However, the extent to which fire affects debris-flow susceptibility in this region is an open question. We documented the occurrence of postfire debris floods and flows following the landfall of a storm that delivered intense rainfall across multiple burn areas. We used this inventory to evaluate the predictive performance of the US Geological Survey M1 likelihood model, a tool that presently underlies the emergency assessment of postfire debris-flow hazards in the western USA. To test model performance, we used the threat score skill statistic and found that the rainfall thresholds estimated by the M1 model for the Central California coast performed similarly to training (Southern California) and testing (Intermountain West) data associated with the original model calibration. Model performance decreased when differentiating between “minor” and “major” postfire hydrologic response types, which weigh effects on human life and infrastructure. Our results underscore that the problem of false positives is a major challenge for developing accurate rainfall thresholds for the occurrence of postfire debris flows. As wildfire activity increases throughout the western USA, so too will the demand for the assessment of postfire debris-flow hazards. We conclude that additional collection of field-verified inventories of postfire hydrologic response will be critical to prioritize which model variables may be suitable candidates for regional calibration or replacement.

California↗
USGS2009

Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes

The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly equally to seasonal and stream-size related variations in the percentage of the stream nitrate flux removed in each watershed.

Biogeochemistry↗
USGS2018

Before the storm: Antecedent conditions as regulators of hydrologic and biogeochemical response to extreme climate events

While the influence of antecedent conditions on watershed function is widely recognized under typical hydrologic regimes, gaps remain in the context of extreme climate events (ECEs). ECEs are those events that far exceed seasonal norms of intensity, duration, or impact upon the physical environment or ecosystem. In this synthesis, we discuss the role of source availability and hydrologic connectivity on antecedent conditions and propose a conceptual framework to characterize system response to ECEs at the watershed scale. We present four case studies in detail that span a range of types of antecedent conditions and type of ECE to highlight important controls and feedbacks. Because ECEs have the potential to export large amounts of water and materials, their occurrence in sequence can disproportionately amplify the response. In fact, multiple events may not be considered extreme in isolation, but when they occur in close sequence they may lead to extreme responses in terms of both supply and transport capacity. Therefore, to advance our understanding of these complexities, we need continued development of a mechanistic understanding of how antecedent conditions set the stage for ECE response across multiple regions and climates, particularly since monitoring of these rare events is costly and difficult to obtain. Through focused monitoring of critical ecosystems during rare events we will also be able to extend and validate modeling studies. Cross-regional comparisons are also needed to define characteristics of resilient systems. These monitoring, modeling, and synthesis efforts are more critical than ever in light of changing climate regimes, intensification of human modifications of the landscape, and the disproportionate impact of ECEs in highly populated regions.

Biogeochemistry↗
USGS2025

Expansion of aquatic and marsh area into once forest and agricultural area reflects changing hydrological conditions along the Upper Mississippi and Illinois rivers (1989-2020)

We examined 30-year trends in the abundance and distribution of aquatic and floodplain vegetation, as well as human land uses in five study reaches of the Upper Mississippi River and one reach of the Illinois River using aerial photography collected in years 1989, 2000, 2010, and 2020. Permanently inundated area increased in all study reaches over the 30-year period. Increases ranged from 0.8% of study reach area in Pool 8 (73 ha) to as much as 6.5% of study reach area in Pool 13 (1,562 ha). Agricultural land use declined in the three study reaches where it was common (>35% of reach area). Agricultural declines ranged from 5.8% of reach area in Pool 26 (2,096 ha) to as much as 15.4% of reach area in the Open River reach (7,121 ha) and corresponded with a similar magnitude increase in permanently inundated area and semi-permanently inundated marsh classes. Total forest area declined in the four northern study reaches of the Upper Mississippi River. Forest loss estimates were on the order of 3.7% of study reach area in Pool 13 (905 ha), 2.1% of Pool 8 (364 ha), and 2.3% of Pool 4 (563 ha). Such losses represent 16.2%, 13.2%, and 10.9% of the total forest area in 1989 in Pools 13, 8 and 4, respectively. Permanently inundated area, wet meadow, shallow marsh vegetation, and mud were the main cover types that replaced forest cover in these reaches. In contrast to the decline in forest cover in the northern reaches, forest cover remained unchanged in the La Grange reach of the Illinois River and increased by 3.5% of study reach area (1,607 ha) in the southern Open River reach of the Mississippi River, mainly in former marsh vegetation and agricultural areas that were acquired by Federal and State agencies. The predominant changes observed across the study system (replacement of agriculture and forest area by permanently inundated area and semi-permanently inundated marsh classes) indicates that hydrological changes have been the main driver of change since 1989 throughout most of the Upper Mississippi and Illinois Rivers. Our study provides an example of changes in a regulated river system driven by regional-scale hydrological changes and local scale restoration actions, changes that could be compared against changes occurring in other large, regulated rivers across the globe.

Illinois, Iowa, Minnesota, Missouri, Wisonsin↗
USGS2017

Hydrologic regimes as potential drivers of morphologic divergence in fish

Fishes often exhibit phenotypic divergence across gradients of abiotic and biotic selective pressures. In streams, many of the known selective pressures driving phenotypic differentiation are largely influenced by hydrologic regimes. Because flow regimes drive so many attributes of lotic systems, we hypothesized fish exhibit phenotypic divergence among streams with different flow regimes. We used a comparative field study to investigate the morphological divergence of Campostoma anomalom (central stonerollers) among streams characterized by highly variable, intermittent flow regimes and streams characterized by relatively stable, groundwater flow regimes. We also conducted a mesocosm experiment to compare the plastic effects of one component of flow regimes, water velocity, on morphology of fish from different flow regimes. We observed differences in shape between flow regimes likely driven by differences in allometric growth patterns. Although we observed differences in morphology across flow regimes in the field, C. anomalum did not exhibit morphologic plasticity in response to water velocity alone. This study contributes to the understanding of how complex environmental factors drive phenotypic divergence and may provide insight into the evolutionary consequences of disrupting natural hydrologic patterns, which are increasingly threatened by climate change and anthropogenic alterations.

Evolutionary Ecology↗
USGS2011

Looking beyond fertilizer: Assessing the contribution of nitrogen from hydrologic inputs and organic matter to plant growth in the cranberry agroecosystem

Even though nitrogen (N) is a key nutrient for successful cranberry production, N cycling in cranberry agroecosystems is not completely understood. Prior research has focused mainly on timing and uptake of ammonium fertilizer, but the objective of our study was to evaluate the potential for additional N contributions from hydrologic inputs (flooding, irrigation, groundwater, and precipitation) and organic matter (OM). Plant biomass, soil, surface and groundwater samples were collected from five cranberry beds (cranberry production fields) on four different farms, representing both upland and lowland systems. Estimated average annual plant uptake (63.3 ± 22.5 kg N ha −1 year −1 ) exceeded total average annual fertilizer inputs (39.5 ± 11.6 kg N ha −1 year −1 ). Irrigation, precipitation, and floodwater N summed to an average 23 ± 0.7 kg N ha −1 year −1 , which was about 60% of fertilizer N. Leaf and stem litterfall added 5.2 ± 1.2 and 24.1 ± 3.0 kg N ha −1 year −1 respectively. The estimated net N mineralization rate from the buried bag technique was 5 ± 0.2 kg N ha −1 year −1 , which was nearly 15% of fertilizer N. Dissolved organic nitrogen represented a significant portion of the total N pool in both surface water and soil samples. Mixed-ion exchange resin core incubations indicated that 80% of total inorganic N from fertilizer, irrigation, precipitation, and mineralization was nitrate, and approximately 70% of recovered inorganic N from groundwater was nitrate. There was a weak but significant negative relationship between extractable soil ammonium concentrations and ericoid mycorrhizal colonization (ERM) rates ( r = −0.22, P < 0.045). Growers may benefit from balancing the N inputs from hydrologic sources and OM relative to fertilizer N in order to maximize the benefits of ERM fungi in actively mediating N cycling in cranberry agroecosystems.

Nutrient Cycling in Agroecosystems↗
USGS2007

Phosphorus budgets in Everglades wetland ecosystems: The effects of hydrology and nutrient enrichment

The Florida Everglades is a naturally oligotrophic hydroscape that has experienced large changes in ecosystem structure and function as the result of increased anthropogenic phosphorus (P) loading and hydrologic changes. We present whole-ecosystem models of P cycling for Everglades wetlands with differing hydrology and P enrichment with the goal of synthesizing existing information into ecosystem P budgets. Budgets were developed for deeper water oligotrophic wet prairie/slough ('Slough'), shallower water oligotrophic Cladium jamaicense ('Cladium'), partially enriched C. jamaicense/Typha spp. mixture ('Cladium/Typha'), and enriched Typha spp. ('Typha') marshes. The majority of ecosystem P was stored in the soil in all four ecosystem types, with the flocculent detrital organic matter (floc) layer at the bottom of the water column storing the next largest proportion of ecosystem P pools. However, most P cycling involved ecosystem components in the water column (periphyton, floc, and consumers) in deeper water, oligotrophic Slough marsh. Fluxes of P associated with macrophytes were more important in the shallower water, oligotrophic Cladium marsh. The two oligotrophic ecosystem types had similar total ecosystem P stocks and cycling rates, and low rates of P cycling associated with soils. Phosphorus flux rates cannot be estimated for ecosystem components residing in the water column in Cladium/Typha or Typha marshes due to insufficient data. Enrichment caused a large increase in the importance of macrophytes to P cycling in Everglades wetlands. The flux of P from soil to the water column, via roots to live aboveground tissues to macrophyte detritus, increased from 0.03 and 0.2 g P m-2 yr-1 in oligotrophic Slough and Cladium marsh, respectively, to 1.1 g P m-2 yr -1 in partially enriched Cladium/Typha, and 1.6 g P m-2 yr-1 in enriched Typha marsh. This macrophyte translocation P flux represents a large source of internal eutrophication to surface waters in P-enriched areas of the Everglades. ?? 2007 Springer Science+Business Media, Inc.

Wetlands Ecology and Management↗
USGS2025

Relating surface water dynamics in wetlands and lakes to spatial variability in hydrologic signatures

The retention of surface water in wetlands and lakes can modify the timing, duration, and magnitude of river discharge. However, efforts to characterize the influence of surface water on discharge regimes have been generally limited to small, wetland-dense watersheds. We developed random forest models to explain spatial variability in six hydrologic signatures, reflecting flashiness, high, and low flow conditions, at 72 gaged watersheds with variable water storage capacity across the conterminous United States. In addition to variables representing meteorology and landscape characteristics, we also tested the inclusion of surface water dynamics, derived from Sentinel-1 and Sentinel-2. Models for all six signatures improved with the addition of catchment characteristics, including surface water dynamics, relative to models with only climate variables. Percent improvement in model adjusted R 2 , mean square error, and Akaike information criterion ranged from 4.00 to 14.33%, 5.00 to 20.30%, and 2.75–8.14, respectively. Automated variable selection can be indicative of the relative importance of certain variables over others. Using a forward selection process, five of the six signature models selected remotely sensed inundation or wetland variables ( p < 0.05). For example, the variable semi-permanent and permanent (SP + P) floodplain inundation (i.e., lakes along rivers) was associated with lower annual flashiness. Further, SP + P non-floodplain waters and geographically isolated wetlands significantly contributed to explaining variability in the low flow signatures. Our findings underscore the capacity of wetlands to stabilize and maintain flows during dry periods. Improved understanding of how surface water dynamics influence hydrologic signatures can inform wetland restoration efforts and facilitate improved resilience to extreme flow conditions.

Wetland Ecology & Management↗
USGS2015

Growth of common brackish marsh macrophytes under altered hydrology and salinity regimes

Coastal marsh plants are increasingly subject to physicochemical stressors under rising sea levels, and the maintenance of marsh ecological functions can depend on the ability of individual species and communities to tolerate or adapt to altered conditions. We conducted a greenhouse experiment to identify hydrology and salinity effects on growth of three common brackish marsh macrophytes of coastal Florida, USA: Distichlis spicata , Juncus roemerianus , and Spartina bakeri . The species were potted as monocultures and exposed to three salinities (0, 15, or 28 psu) and two hydrologic conditions (saturated, tidal) over 22 months. Final stem density of J. roemerianus and S. bakeri did not differ among treatments. In D. spicata , however, stem density was lowest at 28 psu and lower in tidal compared to saturated conditions. Mean stem height of all species was lowest at 28 psu. Aboveground biomass of J. roemerianus was not affected by the treatments, but in D. spicata and S. bakeri it was lowest at 28 psu. Results indicated that J. roemerianus was the most adaptable species and may, therefore, be more resilient to climate-change driven stressors. However, plant-plant interactions such as interspecific competition and facilitation can alter the response of individual species to environmental factors.

Florida↗
USGS2019

Effect of hydrologic, geomorphic, and vegetative conditions on avian communities in the Middle Rio Grande of New Mexico

We evaluated relationships among hydrogeomorphology, vegetation structure and composition, and avian communities among three subreaches of the San Acacia Reach of the Middle Rio Grande (MRG) River of New Mexico. The subreaches varied in degradation, with Subreach 1 being severely entrenched and hydrologically disconnected, Subreach 2 being the least impacted, and Subreach 3 being intermediately disturbed. Avian point count and habitat surveys were conducted to determine avian community structure and abundance, geomorphic feature, surface flooding, and vegetation structure and composition. Ground-nesting birds and low shrub-nesting birds were insensitive to hydrogeomorphic changes as they do not rely on native understory but can use exotic understory or woody debris. In contrast, canopy-nesting birds required native overstory; therefore, they were sensitive to hydrogeomorphic changes as native overstory species require surface floods to germinate and establish. Additionally, native overstory did not vary as expected as the moderately impacted subreach, Subreach 3, had more native overstory ( x &#x00AF; "> x¯ = 30.04%, SE = ±4.57) than the least disturbed subreach, Subreach 2 ( x &#x00AF; "> x¯ = 11.20%, SE = ±1.96). These findings were a result of temporal asynchrony between hydrogeomorphic conditions and overstory composition. No subreach is unaltered and all have been affected by the hydrologic and geomorphic changes on the MRG.

New Mexico↗
USGS2020

Legacy effects of hydrologic alteration in playa wetland responses to droughts

Wetland conservation increasingly must account for climate change and legacies of previous land-use practices. Playa wetlands provide critical wildlife habitat, but may be impacted by intensifying droughts and previous hydrologic modifications. To inform playa restoration planning, we asked: (1) what are the trends in playa inundation? (2) what are the factors influencing inundation? (3) how is playa inundation affected by increasingly severe drought? (4) do certain playas provide hydrologic refugia during droughts, and (5) if so, how are refugia patterns related to historical modifications? Using remotely sensed surface-water data, we evaluated a 30-year time series (1985–2015) of inundation for 153 playas of the Great Basin, USA. Inundation likelihood and duration increased with wetter weather conditions and were greater in modified playas. Inundation probability was projected to decrease from 22% under average conditions to 11% under extreme drought, with respective annual inundation decreasing from 1.7 to 0.9 months. Only 4% of playas were inundated for at least 2 months in each of the 5 driest years, suggesting their potential as drought refugia. Refugial playas were larger and more likely to have been modified, possibly because previous land managers selected refugial playas for modification. These inundation patterns can inform efforts to restore wetland functions and to conserve playa habitats as climate conditions change.

Nevada, Oregon↗
USGS2024

Modeling the responses of blue carbon fluxes in Mississippi River Deltaic Plain brackish marshes to climate change induced hydrologic conditions

Carbon fluxes in tidal brackish marshes play a critical role in determining coastal wetland carbon sequestration and storage, thus affecting carbon crediting of coastal wetland restoration. In this study, a process-driven wetland biogeochemistry model, Wetland Carbon Assessment Tool DeNitrification-DeComposition was applied to nine brackish marsh sites in Mississippi River (MR) Deltaic Plain to examine the responses of gross primary productivity (GPP), ecosystem respiration (ER), net ecosystem exchange (NEE), and emissions of methane (CH 4 ) and nitrous oxide (N 2 O) to climate change. Simulations of a normal hydrologic year (2013), dry year (2011) and wet year (2021), and a hypothetical sea level rise (SLR) case were conducted as climate change scenarios. These climate change scenarios were determined by the Palmer Drought Severity Index (PDSI) for the Northeast Division of Coastal Louisiana during 2001–2021. Model results showed that GPP, ER, NEE, CH 4 , and N 2 O vary with site, and these brackish marshes lost carbon (net CO 2 emission) due to large reduction in primary productivity under the climate scenarios, as well as even during the normal hydrologic year. Average cross-site NEE were 148, 140 and 132 g C m −2 yr −1 in the dry, wet, and normal years (all net loss of wetland C). Under the hypothetical SLR, NEE were reduced by -25% compared to the normal year, but GPP and NPP were declined by -40% and -70%, respectively. These results suggest that climate change induced changes in soil salinity and water table depth will exacerbate carbon loss from tidal brackish marshes.

Louisiana↗