Mississippi River Delta Research Articles

NO2 emissions from oil refineries in the Mississippi Delta

Of the >17,943 thousand barrels per calendar day (bbl/d) of oil refining capacity located in the US, the Petroleum Administration for Defense District 3 (PADD-3) region has the largest number of refineries and accounts for >53 % (or 9607 tbbl/d) of all US oil refining capacity. Processing facilities in this area are mainly located on the Gulf of Mexico coast in Texas and Louisiana. This study selected a sub-region for analysis within the Mississippi River delta in the state of Louisiana between the cities of New Orleans and Baton Rouge. This region is characterized by intensive industrial activity connected with oil refining and related activities. The TROPOspheric Monitoring Instrument (TROPOMI) detected highly localized NO2 vertical column densities (VCDs) over the two largest US refineries in Baton Rouge (503,000 bbl/d) and Garyville (578,000 bbl/d). TROPOMI NO2 VCD over these stations were 100 μmol/m2 and 80 μmol/m2, respectively. A high correlation coefficient (r = 0.65, p < 0.05) was also found between TROPOMI NO2 and population density. Data from the National Emissions Inventory (NEI) showed high NOx emissions from refineries and other industries including coal-fired power generation, chemical, and aluminum processing plants. The results of the NO2 analysis are of practical interest for a comparative assessment of air pollution, as well as for the exchange of best practices in the field of low-waste fuel combustion technologies.

Drivers of diatom production and the legacy of eutrophication in two river plume regions of the northern Gulf of Mexico

In the northern Gulf of Mexico (nGoM), the Louisiana Shelf (LS) and Mississippi Bight (MB) subregions are influenced by eutrophication to varying degrees. Despite recognition that dissolved silicon may regulate diatom productivity in the nGoM, there is only one published data set reporting biogenic silica (bSiO2) production rates for each subregion. We report that bSiO2 production rates on the LS and MB are high and appear to be controlled by different nutrients among seasons. Despite exceptional upper trophic level biomass regionally, which suggests significant primary production by diatoms (as in other systems), gross euphotic-zone integrated bSiO2 production rates are lower than major bSiO2 producing regions (e.g. upwelling systems). However, when normalizing to the depth of the euphotic zone, the bSiO2 production rates on the LS are like normalized rates in upwelling systems. We suggest local river-plume influenced hydrography concentrates diatom productivity within shallow euphotic zones, making production more accessible to higher trophic organisms. Comparison of rates between the LS and MB suggest that the fluvial nitrate within the LS stimulates bSiO2 production above that in the MB, which has a smaller watershed and is less eutrophic (relatively). Beyond understanding the factors controlling regional bSiO2 production, these data offer the most comprehensive Si-cycle baseline to date as the LS and MB will likely exchange freely in the mid to late century due to land subsidence of the Mississippi River delta and/or sea-level rise.

Dissolved organic carbon dynamics and fluxes in Mississippi-Atchafalaya deltaic system impacted by an extreme flood event and hurricanes: a multi-satellite approach using Sentinel-2/3 and Landsat-8/9 data

Transport of riverine and wetland-derived dissolved organic carbon (DOC) spanning tidal wetlands, estuaries, and continental shelf waters functionally connects terrestrial and aquatic carbon reservoirs, yet the magnitude and ecological significance of this variable and its spatiotemporal linkage remains uncertain for coastal deltaic regions, such as Mississippi River Delta Plain, which includes Mississippi (MR) and Atchafalaya (AR) rivers and estuaries with vast expanses of wetlands and coastal forests. We examined DOC dynamics and fluxes in this large river-dominated wetland-estuarine system for the period between 2019 and 2021 that included an extreme river flood event in 2019, two major hurricanes (Barry in 2019 and Ida in 2021), and cold front passage using an improved adaptive quasi-analytical algorithm (QAA-AD) applied to multi-satellite sensors (Sentinel 3A/B OLCI, Landsat-8/OLI and Sentinel-2A/B MSI) with varying spectral and spatial (10/30/300 m) resolutions. The DOC estimates from multi-satellite sensors in combination with water fluxes were used to assess DOC fluxes from two large rivers (MR and AR) and small channels across the delta plain. Overall, this system delivered a total of 6.7 Tg C yr-1(1 Tg = 1012g) into the estuarine zone and the northern Gulf of Mexico (nGoM) during 2019. High DOC fluxes from the AR (1.3 Tg C yr-1) and MR (4.5 Tg C yr-1) were associated with the extreme flood event in 2019. Hurricanes that occurred in the study period also contributed to the wetland and estuarine DOC fluxes into continental shelf waters; for example, the passage of Hurricane Barry in July 2019, delivered over a 3-day period ~1.33 ×109g DOC from Barataria Basin into the nGoM. Sentinel 2-MSI land and water classification revealed that Hurricane Ida eroded a total of 1.34×108m2of marshes in middle Barataria Basin, converting those habitats into open water with 3.0 m inundation depth and high DOC concentrations (16.4 mg L-1), a potentially large DOC source to the coastal waters. Overall, storms and flood events are major sources of DOC flux that facilitate transport of upstream carbon as well as transformation of carbon in the wetlands, through the conversion of vegetated wetland to open water.

Floating Debris in the Northern Gulf of Mexico after Hurricane Katrina.

Hurricane Katrina (category 5 with maximum wind of 280 km/h when the eye is in the central Gulf of Mexico) made landfall near New Orleans on August 29, 2005, causing millions of cubic meters of disaster debris, severe flooding, and US$125 billion in damage. Yet, despite numerous reports on its environmental and economic impacts, little is known about how much debris has entered the marine environment. Here, using satellite images (MODIS, MERIS, and Landsat), airborne photographs, and imaging spectroscopy, we show the distribution, possible types, and amount of Katrina-induced debris in the northern Gulf of Mexico. Satellite images collected between August 30 and September 19 show elongated image features around the Mississippi River Delta in a region bounded by 92.5°W-87.5°W and 27.8°N-30.25°N. Image spectroscopy and color appearance of these image features indicate that they are likely dominated by driftwood (including construction lumber) and dead plants (e.g., uprooted marsh) and possibly mixed with plastics and other materials. The image sequence shows that if aggregated together to completely cover the water surface, the maximal debris area reached 21.7 km2 on August 31 to the east of the delta, which drifted to the west following the ocean currents. When measured by area in satellite images, this perhaps represents a historical record of all previously reported floating debris due to natural disasters such as hurricanes, floodings, and tsunamis.

Image-based machine learning for monitoring the dynamics of deltaic islands in the Atchafalaya River Delta Complex between 1991 and 2019

Deltaic islands are distinct hydro-environmental zones with global significance in food security, biodiversity conservation, and fishery industry. These islands are the fundamental building blocks of many river deltas. However, deltaic islands are facing severe challenges due to intensive anthropogenic activities, sea level rise, and climate change. In this study, dynamic changes of deltaic islands in Wax Lake Delta (WLD) and Atchafalaya Delta (AD), part of the Atchafalaya River Delta Complex (ARDC) in Louisiana, USA, were quantified based on remote sensing images from 1991 to 2019 through a machine learning method. Results indicate a significant increase in deltaic islands area for the whole ARDC at a rate of 1.29 km2/yr, with local expansion rates of 0.60 km2/yr for WLD and 0.69 km2/yr for AD. All three parts of the WLD naturally prograded seaward, with the western part (WP) and central part (CP) expanding southwestward to the sea, while the eastern part (EP) prograding southeastwards. Differently from WLD, the three parts of AD irregularly expanded seaward under the impacts of anthropogenic activities. The WP and CP of the AD expanded respectively northwestwards and southwestwards, while the EP remained stable. Different drivers dominate the growth of deltaic islands in the WLD and AD. Specifically, fluvial suspended sediment discharge and peak flow events were responsible for the shift in the spatial evolution of WLD, while dredging and sediment disposal contributed to the expansion of AD. Tropical storms with different intensity and landing locations caused short-term deltaic island erosion or expansion. Tropical storms mainly generated erosion on the deltaic islands of the WLD, while causing transient erosion or siltation on the deltaic islands of the AD. In addition, high-intensity hurricanes that made landfall east of the deltas caused more erosion in the AD. Finally, sea level rise, at the current rate of 8.17 mm/yr, will not pose a threat to the deltaic island of WLD, while the eastern part of AD may be at risk of drowning. This study recognizes the complexity of factors influencing the growth of deltaic islands, suggesting that quantitative studies on the deltaic island extent are of critical for the restoration and sustainable management of the Mississippi River Delta and other deltas around the world.

Bird predation on Roseau cane scale as revealed by a web image search and querying a citizen monitoring database

AbstractAn invasion of Roseau cane scale, Nipponaclerda biwakoensis, native to East Asia, is associated with recent widespread dieback of common reed stands in the Mississippi River Delta, Louisiana. A previous study suggested that, in its native range, the combined mortality from Common Reed Bunting Emberiza schoeniclus and parasitoid wasps may control the abundance of Roseau cane scale. However, there is limited knowledge about which other bird species may prey on Roseau cane scale or the feeding patterns of these birds. Here we used web search and citizen science monitoring data to tabulate bird predation events on Roseau cane scales across sites in Japan and determine which bird species may be the most important predators and when the observed feeding typically occurs. We scanned web entries using both Google image searches and the social networking services including Twitter, Instagram, and Facebook. Additionally, we accessed long‐term field observation records obtained by volunteer monitoring conducted by the members of the Kanagawa Branch of the Wild Bird Society of Japan. By using these citizen science approaches, we detected 16 bird species, mainly Common Reed Bunting but also other migratory and resident species, preying on the Roseau cane scale in reed beds throughout central Japan and most detection occurred during the winter. This study demonstrates that biological information obtained from publicly available data from citizen observers can be useful for exploring ecological patterns of various species including potential predators against invasive species.

Cultural-ecosystem resilience is vital yet under-considered in coastal restoration

As large areas of the Mississippi River Delta (MRD) of the USA disappear into the sea, present-day communities and cultural resources are lost. While the land loss may be readily quantified, describing the impact of cultural losses is less straightforward because cultural elements are frequently less tangible and difficult to map, identify, and categorize. The elision of cultural components of landscapes and ecosystems is evident in restoration practices and policies, although numerous scholars have identified the interlinked processes of culture and ecology as critical to rebuilding healthy and resilient environments. We define and measure cultural-ecosystem resilience (CER) in the Mississippi River Delta through analyses of Indigenous oral histories, mound-building practices and settlement patterns, and the persistence and reuse of archaeological sites. CER describes a system containing resilient properties embedded in human-natural settings including river deltas that may manifest in oral cultural traditions, architecture, and the selection of habitable environments. Our interdisciplinary approach demonstrates the role of human-modified landscapes in generating resilience for past and present coastal communities and highlights the importance of consulting records of historic and modern Indigenous traditions in shaping sustainable landscape-management strategies. Results show that archaeological earthen and shell mounds made by Native American Gulf Coast and MRD communities have been persistent features that endured for centuries and are sited in regions of high multicultural value within the dynamic delta. Yet, we document the rapid 20th-century loss of mounds due to coastal erosion, industry, and other human land-use practices. Present-day and future coastal land loss endangers what remains of these keystone features and thus lowers the resilience of modern Mississippi River Delta communities.

Whole Stand Variable Density Yield Equations for Oak-Gum-Cypress Bottomland Hardwood Forests

Abstract Variable density yield equations were constructed using fuzzy linear regression for bottomland oak-gum-cypress forests along the US Gulf Coast and lower Mississippi River Delta region. The USDA Forest Service (Forest Service)’s Forest Inventory and Analysis program provided plot data (n = 526). Predictors included stand age, growing stock basal area per acre, sweetgum site index (base age 50 years), and US Environmental Protection Agency ecoregion dummy variables located in Alabama, Arkansas, Louisiana, Mississippi, Tennessee, and Texas. Dependent variables were per acre growing stock cubic foot yield (GSV) and Doyle board foot sawlog yield (SLV). Plots averaged 58 years, 90 ft2/ac basal area, 79 ft site index, 2,556 ft3/ac GSV, and 11,183 Doyle bf/ac SLV. Adjusted R2 were 0.98 (GSV) and 0.77 (SLV). Basal area possessed fuzziness in the GSV model, whereas the SLV model’s intercept was fuzzy. Six ecoregions possessed fuzziness in each model, but these were not identical across models.

The concept of land bridge marshes in the Mississippi River Delta and implications for coastal restoration

Louisiana has high coastal wetland loss rates due to natural processes such as subsidence and anthropogenic activities such as construction of river levees and dams, pervasive alteration of surface hydrology by local industries such as oil and gas, and navigation. With the exception of the Atchafalaya River discharge area, most of Louisiana's marsh coastline is retreating and coastal marshes are degrading. In the inactive degrading delta regions, there exists a previously uncharacterized landform referred to colloquially as coastal ‘land bridge’ marshes. Land bridge marshes are saline or brackish marshes fronting large estuarine bays or lakes with sufficient fetch and wave energy to supply high levels of resuspended sediments to the marsh surface. They are generally linear features that are oriented parallel to the coast and the shoreline front retreats landward due to erosion from wave energy. These marshes persist over time vertically due to input of resuspended sediments but are experiencing rapid edge erosion due to wave attack. Comparison of data from Louisiana's Coastal Reference Monitoring System (CRMS) sites show that land bridge marshes have a greater frequency of higher soil surface elevation and higher soil bulk density than non-land bridge marshes. Because land bridges are vertically stable relative to other coastal wetlands, identification of measures to sustain these landscape features is important. Simulations using MarshMorpho2D, a process-based reduced-complexity morphology model, suggest that protection barriers installed on the seaward side of land bridge marshes will attenuate wave energy and, thus, edge erosion. Shoreline protection that can reduce wave energy but still allow sediment input to marshes include living shorelines, rock barriers, and/or breakwaters. Periodic thin layer nourishment of the marsh surface may be necessary to help sustain vertical growth. Further, marsh creation projects directly landward of land bridge marshes may benefit from their protection from waves and as a source of sediment. Consideration of land bridge marshes as distinct marsh types in the State Master Plan and integrated modeling could help to identify measures to sustain these landscape features.

Vegetation‐Driven Seasonal Sediment Dynamics in a Freshwater Marsh of the Mississippi River Delta

AbstractDeltaic wetlands are critically important coastal environments, upon which hundreds of millions of people depend. Managing and preserving them in the face of sea level rise will be a challenging task over the next century that will require land managers to devise restoration strategies that maximize the delivery and storage of mineral sediments, and to apportion limited sediment resources to priority locations. We collected a unique field data set characterizing sediment delivery to, and retention in, a deltaic wetland throughout a period of rapidly changing emergent and submerged vegetation conditions in the spring of 2019. Our results demonstrate that wetland deposition is extremely sensitive to the timing of the flood pulse with respect to vegetation conditions, and that vegetation alone can adjust sediment delivery and retention by one or more orders of magnitude over a period of weeks. In planning for wetland management operations, it will be critical for managers to assess these rapidly changing conditions as they influence project success.

Measuring biodiversity and the loss of indigenous landscapes in coastal Louisiana using airborne imagery and satellite data

ABSTRACT The Adams Bay site is a Native American monumental centre located in the Mississippi River Delta (MRD), a dynamic, geomorphic environment comprised of marshes, bayous, and rivers. The site itself was constructed approximately 600 to 800 years ago by Indigenous communities who are the ancestors of modern-day coastal communities. Earthen mounds at Adams Bay have disappeared over the past 70 years, and the last remaining mound at the site has almost completely eroded away over the past 10 years. This is an environment that is rapidly subsiding, eroding, and becoming inundated due to sea-level rise, and within this environment are hundreds of earthen and shell mounds. This study uses Sentinel-2 and National Agriculture Imagery Program data to document decadal changes to the landscape at Adams Bay and posits that mound-building had net positive impacts on biodiversity and vegetation in this marshy, deltaic environment. Sites like Adams Bay provide remarkable ecosystem services, enhancing the resilience of coastal ecosystems, and they must be studied and/or preserved before being lost to climatic and environmental forces. Finally, these sites are still incredibly significant to modern Indigenous communities who live in the coastal zone today, and additional resources need to be dedicated towards their conservation.

Potential methane production in oligohaline wetlands undergoing erosion and accretion in the Mississippi River Delta Plain, Louisiana, USA

Methane (CH4) is steadily increasing in the atmosphere from different sources including wetlands. However, there is limited landscape level CH4 flux data in deltaic coastal systems where the availability of freshwater is impacted by the combined effect of climate change and anthropogenic impacts. Here we determine potential CH4 fluxes in oligohaline wetlands and benthic sediments in the Mississippi River Delta Plain (MRDP), which is undergoing the highest rate of wetland loss and most extensive hydrological wetland restoration in North America. We evaluate potential CH4 fluxes in two contrasting deltaic systems, one undergoing sediment accretion as result of a freshwater and sediment diversions (Wax Lake Delta, WLD), and one experiencing net land loss (Barataria-Lake Cataouatche, BLC). Short- (<4 days) and long-term (36 days) incubations using soil and sediment intact cores and slurries were performed at different temperatures representing seasonal differences (10, 20, 30 °C). Our study revealed that all habitats were net sources of atmospheric CH4 in all seasons, and CH4 fluxes were generally the highest for the 20 °C incubation. The CH4 flux was higher in the marsh habitat of the recently formed delta system (WLD) with total carbon content of 5–24 mg C cm−3 compared to the marsh habitat in BLC, which had high soil carbon content of 67–213 mg C cm−3. This suggests that the quantity of soil organic matter might not be a determining factor in CH4 flux. Overall, benthic habitats were found to have the lowest CH4 fluxes indicating that projected future conversions of marshes to open water in this region will impact the total wetland CH4 emission, although the overall contribution of such conversions to the regional and global carbon budgets is still unknown. Further research is needed to expand the CH4 flux studies by simultaneously using several methods across different wetland habitats.

Land loss due to human-altered sediment budget in the Mississippi River Delta

Land loss due to human-altered sediment budget in the Mississippi River Delta

Land loss in the Mississippi River Delta: Role of subsidence, global sea-level rise, and coupled atmospheric and oceanographic processes

Land loss in the Mississippi River Delta: Role of subsidence, global sea-level rise, and coupled atmospheric and oceanographic processes

Can biodiversity of preexisting and created salt marshes match across scales? An assessment from microbes to predators

AbstractCoastal wetlands are rapidly disappearing worldwide due to a variety of processes, including climate change and flood control. The rate of loss in the Mississippi River Delta is among the highest in the world and billions of dollars have been allocated to build and restore coastal wetlands. A key question guiding assessment is whether created coastal salt marshes have similar biodiversity to preexisting, reference marshes. However, the numerous biodiversity metrics used to make these determinations are typically scale dependent and often conflicting. Here, we applied ecological theory to compare the diversity of different assemblages (surface and below‐surface soil microbes, plants, macroinfauna, spiders, and on‐marsh and off‐marsh nekton) between two created marshes (4–6 years old) and four reference marshes. We also quantified the scale‐dependent effects of species abundance distribution, aggregation, and density on richness differences and explored differences in species composition. Total, between‐sample, and within‐sample diversity (γ, β, and α, respectively) were not consistently lower at created marshes. Richness decomposition varied greatly among assemblages and marshes (e.g., soil microbes showed high equitability and α diversity, but plant diversity was restricted to a few dominant species with high aggregation). However, species abundance distribution, aggregation, and density patterns were not directly associated with differences between created and reference marshes. One exception was considerably lower density for macroinfauna at one of the created marshes, which was drier because of being at a higher elevation and having coarser substrate compared with the other marshes. The community compositions of created marshes were more dissimilar than reference marshes for microbe and macroinfauna assemblages. However, differences were small, particularly for microbes. Together, our results suggest generally similar taxonomic diversity and composition between created and reference marshes. This provides support for the creation of marsh habitat as tools for the maintenance and restoration of coastal biodiversity. However, caution is needed when creating marshes because specific building and restoration plans may lead to different colonization patterns.

Live-Dead Shifts in Molluscan Functional Diversity in Coastal Alabama

Abiotic and biotic environmental factors shape species behavioral, physiological, and morphological traits. Shifts in the diversity of these functional traits therefore can serve as an indicator of spatial and temporal changes in environmental conditions. In recent centuries, the delivery of nutrients to coastal ecosystems has increased markedly through changing waste management and land-use practices. Nutrient enrichment has increased rates of primary productivity, resulting in greater organic accumulation on the seafloor and the development of hypoxic conditions in some areas, due to the aerobic decomposition of phytoplankton blooms. Anthropogenic eutrophication and associated hypoxia have been monitored annually in the northern Gulf of Mexico for over four decades, with an emphasis on areas surrounding the Mississippi River Delta. To further understand how anthropogenic eutrophication affects functional diversity in benthic marine communities, we collected live and dead assemblages of bivalve mollusks from surficial sediments at five stations along the -20 meters isobath in coastal Alabama. Bivalves were categorized into functional groups using information about their mobility, fixation, feeding type, substrate preference, and body size. Consistent with our hypotheses, preliminary results indicate a temporal shift from benthic communities dominated primarily by epifaunal and infaunal suspension-feeding species to communities characterized primarily by deposit feeders, many of which dwell on the seafloor surface. Ongoing analyses will help identify the functional traits that are most sensitive to these changing environmental conditions. Understanding functional diversity shifts in the recent past can provide insight into how anthropogenic eutrophication may further impact benthic marine ecosystems in the future.

Interactions among science, environmental policy and public perception in a Mississippi River Delta assimilation wetland

In November 2006, the City of Hammond, Louisiana, began discharging secondarily treated, disinfected municipal effluent through a distribution pipeline to a 14,000 ha emergent wetland complex referred to as the East Joyce Wetlands. The primary goals were to improve local water quality by taking effluent that would normally be discharged to local waterways and directing it to wetlands that were hydrologically isolated and degraded by saltwater intrusion. During the 2007 growing season there was robust growth of marsh vegetation with a near doubling of productivity compared to controls, however, during winter 2007 there was a massive decline in vegetation and transition to open water in the 121 ha of wetlands in the direct path of effluent discharge. Herbivory by nutria was found to be the cause of the decline, but not before several other causes were hypothesized and largely accepted by the public, specifically that the cause of the vegetation decline was due to excess nutrients that increased rates of soil decomposition and limited root growth of plants. Studies show these hypotheses were flawed due to scale and methodology issues. Intensive nutria removal began in the spring of 2008 and continued through the winter of 2008–2009, with approximately 2000 nutria killed, and vegetation recovery began during the spring of 2009, which was most pronounced and consistent nearest the discharge pipe. Vegetative cover increased dramatically from the near complete loss after nutria grazing to near 80% by 2015, and wetland recovery has continued to the present.

Sources and chemical stability of soil organic carbon in natural and created coastal marshes of Louisiana

Coastal marshes are globally important for sequestering carbon, yet sea-level rise and anthropogenic stressors can reduce their capacity as carbon sinks. Marsh restoration can offset a portion of carbon loss through the degradation of natural marshes, but potential differences in the sources and stability of soil organic carbon (SOC) between created and natural marshes may affect their function as a long-term carbon sink. Here, we examine the sources and chemical stability of SOC in natural and created marshes across the Gulf coast of Louisiana, USA. Marshes were examined along an estuarine salinity gradient in a former interdistributary basin of the Mississippi River Delta and in six created marshes across a 32-year chronosequence and a natural reference marsh (n = 6) in the Chenier Plain. Carbon source was assessed using δ13C analysis and chemical stability was determined through an acid hydrolysis digestion that removed labile carbon (LC). Soil δ13C values suggested that the local vegetation dominated SOC in all natural marshes although brackish marshes had a mix of sources and degradation of SOC. Recalcitrant carbon (RC) was 72.2 ± 0.5 % of SOC across fresh, brackish and saline marshes. The depth-averaged RC accumulation rate was almost three times greater than LC accumulation rate, yet both contributed significantly to accretion and long-term SOC accumulation (124–132 g m−2 y−1 in natural marshes). RC and SOC accumulation rate increased with mineral sediment accumulation rate. For the created marshes, SOC became increasingly recalcitrant due to an increase in in-situ plant inputs, but accumulation rates were lower than the natural marshes. Overall, this study illustrates that natural marshes have a large stock of RC from the vegetation while dredge sediment created marshes have no plant-derived carbon initially, which accumulates slowly thereafter. Restoration practices may be improved by preserving and augmenting these deteriorating but carbon-rich natural marshes.

CLIMATE CHANGE, MITIGATION OF FLOODS AND DROUGHTS: ONLINE INFORMATIVE AND EDUCATIONAL RESOURCES

According to projections, in many regions of the world, heavy rains interspersed with long lasting dry periods are to be expected as a consequence of climate change, which requires adaptation strategies. In fact, dry soils have no time to soak heavy rains that fall quickly, the groundwater resources are not replenished and the aquifers are declining. At the same time, flood prone areas may suffer floods. Notoriously, this is already happening. In the meanwhile shrinking glaciers, and dam reservoirs that lose storage capacity as a consequence of sediment accumulation, further limit water availability downstream. In addition, coastal areas deprived of the sediments trapped in the reservoirs, undergo land losses; the Mississippi river delta has already lost 4,800 km², an area roughly the size of Delaware. The siltation of dam reservoirs can be mitigated; in this regard, several techniques are presented. The intensive exploitation of an aquifer, combined with a limited replenishment, may result in, e.g. land subsidence and seawater intrusion. Several techniques aimed at enhancing the recharge of aquifers, harvesting rainwater and saving water are presented in the article. Urban structures, such as rain gardens, bioswales, permeable asphalt and permeable pavements allow rainwater to infiltrate into the soil, thus recharging aquifers and mitigating overland runoff and floods. Several documents presented in the article deal with improving the liveability of cities, increasingly crowded and hot, thanks to a more efficient water management and planting trees. Our dietary choices, the clothes we wear and the food we waste have an influence on the overexploitation of water resources, sometimes in producing countries very far away from our country.&lt;p&gt; &lt;/p&gt;&lt;p&gt;&lt;strong&gt; Article visualizations:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;img src="/-counters-/edu_01/0261/a.php" alt="Hit counter" /&gt;&lt;/p&gt;

Coastal wetland area change for two freshwater diversions in the Mississippi River Delta

Coastal systems around the globe are being re-integrated with adjacent river systems to restore the natural hydrologic connection to riparian wetlands. The Mississippi River sediment diversions or river reconnections are one such tool to combat high rates of wetland loss in coastal Louisiana, USA by providing freshwater, sediment, and nutrients. There has been some disagreement in the published literature whether re-establishing river reconnection is slowing or contributing to coastal wetland loss. This issue is due to the difficulties in the application of remote sensing in low-relief environments where water level changes could indicate either land loss or simply temporary submergence. We analyzed land change at the receiving areas of two existing freshwater river diversions, Davis Pond and Caernarvon, which have been intermittently receiving river water for up to 2+ decades. This study provides a robust analysis of wetland land change rates in proximity these river diversions including years before river reconnection. Our analyses indicate a net land gain since river reconnection operations began at Davis Pond Diversion (+3.42 km2; range: +2.02–4.81 km2) and no statistically significant change at the Caernarvon Diversion. The Davis Pond wetland results are corroborated with data from a decadal field study documenting increased inorganic sedimentation in the soil. It is clear from this study and others, that river reconnection can increase or, in the case of Caernarvon, have no statistical effect on the land change in these systems due to differences in vegetation, hydroperiod, sediment delivery and external factors including hurricane impacts. Our remote sensing analysis was compared with a global water area change analysis mapping tool which also supported our findings.