Agricultural Floodplain Research Articles

Towards sustainable agricultural landscapes: Lessons from an interdisciplinary research-based framework applied to the Saint Lawrence floodplain

Floodplains are unique environments that provide a dynamic link between terrestrial and aquatic systems. Intensification of human activity – particularly agriculture and urbanisation – has resulted in the degradation of floodplains worldwide. Restoration and sustainable management of floodplains requires holistic assessment and compromise between stakeholders to successfully balance environmental, economic, and social benefits. Yet, understanding these complex systems sufficiently to provide evidence-based recommendations is a challenge. We present the lessons learned from establishing an interdisciplinary research-based framework on the agricultural floodplain of Lake Saint Pierre, Québec, Canada, whose mandate was to a) understand and define key environmental, agricultural, and socioeconomic attributes of the landscape, b) quantify the trade-offs and synergies between these attributes across different agricultural practices, regions, and land uses, and c) explore novel agri-environmental management practices to assess their role in sustainable floodplain management. Within this manuscript, we explore the benefits that such an approach offers in evaluating sustainable floodplain land use. We found that an interdisciplinary research-based approach demonstrated important benefits such as knowledge transfer, more efficient use of resources (e.g., personnel, funding), and a flexible yet robust research framework. A framework of individual research projects connected to broader interdisciplinary themes allowed a more holistic synthesis of the floodplain systems and assessment of agri-environmental practices. By implicitly considering spatial and social scales, we conceptualised not just how redistribution of the land use types can meet sustainable management objectives, but also explored how compromises within existing uses can optimise socio-economic, agricultural and environmental dimensions and move towards a sustainable multifunctional landscape.

Fish conservation in streams of the agrarian Mississippi Alluvial Valley: conceptual model, management actions, and field verification

The effects of agriculture and flood control practices accrued over more than a century have impaired aquatic habitats and their fish communities in the Mississippi Alluvial Valley, the historic floodplain of the Lower Mississippi River prior to leveeing. As a first step to conservation planning and adaptive management, we developed and tested a conceptual model of how changes to this floodplain have affected stream environments and fish assemblages. The model is deliberately simple in structure because it needs to be understood by stakeholders ranging from engineers to farmers who must remain engaged to ensure effective conservation. Testing involved multivariate correlative analyses that included descriptors of land setting, water quality, and fish assemblages representing 376 stream samples taken over two decades and ranging in Strahler stream order from 1 to 8. The conceptual model was adequately corroborated by empirical data, but with unexplained variability that is not uncommon in field surveys where gear biases, temporal biases, and scale biases prevent accurate characterizations. Our conceptual model distinguishes three types of conservation actions relevant to large agricultural floodplains: reforestation of large parcels and riparian zone conservation, in-channel interventions and connectivity preservation, and flow augmentation. Complete restoration of the floodplain may not be an acceptable option to the agriculture community. However, in most cases the application of even the most basic measures can support the return of sensitive aquatic species. We suggest that together these types of conservation actions can bring improved water properties to impacted reaches, higher reach biodiversity, more intolerant species, and more rheophilic fishes.

Assessing climate change scenarios in the Amazon Basin: a risk governance model

The impacts of climate change are becoming more severe and can only be addressed through governance that spans from local to global levels. To enhance adaptation and response strategies, we need to integrate the knowledge of local communities and improve institutional and state capacity. In the Amazon Basin, current plans for adaptation and response only consider a global perspective, without any input from local communities. By including the region-specific knowledge of these communities, we can better identify the risks related to climate change. The research aimed to answer the question of how to integrate these specificities in an operational risk governance model. We developed an operational risk governance model for Amazon (R-GOMAM) that explores cross-scale interplay and risk identification related to climate change. It provides a comprehensive perspective of risk governance across different scales. A combination of methods was used to integrate the quantitative and qualitative dimensions of data collection and analysis. Additionally, we applied fuzzy logic, to synthesize the cross-scale interplay model. The model was able to account for all dimensions of the Amazon Basin countries, including dryland agriculture, floodplain agriculture, vegetable extraction, fishing, animal breeding, water quality, and household infrastructure. It considered the complexity and uncertainty of risk governance, identified hazard scenarios, and determined the level of risk in the region. Our evaluation of institutional and state capacity in the Purus River Basin revealed insufficient regulations and institutional mechanisms to address climate change risks. Our model identifies different scenarios of hazards and determines the degree of risk in the Amazon Basin countries. Prior models for Brazilian regions overlooked local differences in institutional and state capacities. Our study fills this gap, serving as a supplement for assessing climate change effects in not just Amazonia but other regions as well.

Short‐ and long‐term legacies of carbon sequestration, and nutrient burial in floodplain wetlands of agricultural and forested catchments, Indiana, United States

AbstractSoil organic carbon (C) sequestration and nitrogen (N) and phosphorus (P) burial were measured in two floodplain wetlands' soils of the West Fork of the White River watershed (Indiana, United States) whose catchments differed in land use to better understand how land use practices affect wetland C and nutrient retention. The catchment of one floodplain, Upper West Fork, is dominated by row crop agriculture (61%) whereas the second catchment, Beanblossom Creek, is mostly forested (85%). Soils (0–30 cm) of the two floodplain wetlands had similar bulk density (1.23 g/cm3). Soil organic C and N were low in both floodplains but the percent organic C and N was two times greater (3.3% C, 0.22% N) in the agricultural floodplain than in the floodplain in the forested catchment (1.5% C, 0.14% N). Soil P was three times greater in the agricultural (1100 μg/g) than in the forested floodplain (350 μg/g). Recent soil accretion based on 137Cs which provides a historical record since 1964 (60 years), was two times greater in the agricultural floodplain (2.2 mm/year) than in the forested catchment (1.0 mm/year). Sediment deposition (2500 g/m2/year), C sequestration (90 g/m2/year), and N burial (7.5 g/m2/year) were three times greater in the agricultural floodplain and P burial was seven times greater (3.0 vs. 0.41 g/m2/year). Long‐term measurements (100 years) based on 210Pb did not show large differences in C sequestration and N burial between the two floodplains though soil accretion and sediment deposition were greater in the forested floodplain. We attribute these higher rates to greater erosion in the watershed before 1950 when the catchment had more agricultural land and before instruction on best management practices to reduce soil erosion. These findings confirm previously published studies that show that P enrichment and accumulation in floodplain soils represent legacy effects of agricultural land use in the catchment.

Shrinking Desert Channel Response to Increasing Human Interferences and Changing Natural Factors in the Upper Yellow River

Many rivers are tightly coupled and intersected with aeolian sand dunes, whose geomorphological evolution involves not only fluvial processes but also aeolian processes that pose a new challenge to fluvial geomorphological studies. However, due to few field studies, our overall understanding of the desert channel geomorphic process is limited. In this paper, we present an outstanding example of desert river channel evolution regulated by aeolian–fluvial interactions in the Ulan Buh Desert of the Yellow River, based on a long time series data set (1966–2019) of channel cross-sections. The results indicate that the lateral addition of aeolian sand, the water–sediment relationship and human interference have a significant role at different periods of channel evolution. Before 1986, higher discharge, lower sediment content and greater intensity of aeolian activity caused aeolian–fluvial interactions and a relative scouring and silting balance in the channel, with little human activity. From 1986 to 2000, an increase in large reservoir operation, vegetation coverage and floodplain farming, coupled with water–sediment relationship variation, caused rapid deposition and shrinkage of the river channel. From 2000 to 2014, the channel kept a slight scouring state. With Haibowan reservoir operation beginning in 2014, the talweg experienced rapid scouring and undercut rebound. However, an expanding and stable floodplain accelerated sedimentation on the floodplain and weakened river lateral erosion, indicating that the channel has shown a shrinkage trend. Meanwhile, wavelet analysis results indicate that human interferences and aeolian activities have no significant role in the periodical characteristics of the channel’s longitudinal erosion and deposition. Therefore, on the whole, increasing human interferences and decreasing wind dynamics have driven this desert wandering channel to be stable, and to gradually form a new balance between erosion and sedimentation.

Temporal Variations in Chemical Proprieties of Waterbodies within Coastal Polders: Forecast Modeling for Optimizing Water Management Decisions

In polder-type land, water dynamics are heavily influenced by the artificial maintenance of water levels. Polders are low-lying areas of land that have been reclaimed from the sea or from freshwater bodies and are protected from flooding by dikes or other types of flood-protection structures. The water regime in polders is typically managed using a system of canals, pumps, and sluices to control the flow of water in and out of the area. In this study, the temporal changes in water salinity in the polder-type agricultural floodplain within the Neretva River Delta (NRD), Croatia, were analyzed by applying multivariate statistics and forecast modelling. The main aim of the study was to test the model that can be used in practice to forecast, primarily, water suitability for irrigation in a coastal low-lying agricultural catchment. The specific aim of this study was to use hydrochemistry data series to explain processes in water salinity dynamics and to test the model which may provide accurate salinity prediction, or finally select the conditions in which the model can be applied. We considered the accuracy of the model, and it was validated using independent data sets. To describe different patterns of chemical changes in different water classes due to their complex hydrological connectivity, multivariate statistics (PCA) were coupled with time-series analysis and Vector Autoregression (VAR) model forecasting. The multivariate statistics applied here did not indicate a clear connection between water salinity of the surface-water bodies and groundwater. The lack of correlation lies in the complex hydrological dynamics and interconnectivity of the water bodies highly affected by the artificial maintenance of the groundwater level within the polder area, as well as interventions in the temporal release of freshwater into the drainage canal network. Not all individual water classes contributed equally to the dominant patterns of ionic species identified by PCA. Apparently, land use and agricultural management practices in the different polders lead to uneven water chemistry and the predominant contributions of specific ions, especially nutrients. After applying the Granger causality test to reveal the causal information and explain hidden relationships among the variables, only two surface-water and two groundwater monitoring locations displayed a strong causal relationship between water electrical conductivity (ECw) as an effect and sea level as a possible cause. The developed models can be used to evaluate and emphasize the unique characteristics and phenomena of low-lying land and to communicate their importance and influence to management authorities and agricultural producers in managing and planning irrigation management in the wider Mediterranean area.

Flooding risk of cropland areas by repiquetes in the western Amazon basin: A case study of Peruvian Tamshiyacu City

Study regionThe western Amazon basin at Tamshiyacu gauging station (near the Iquitos City) hosts floodplain agriculture that can be affected by the sudden reversal in direction of water levels known as “repiquetes” that produce intermittent flooding. Study focusThis study assesses repiquete flooding risk in riparian crop areas based on statistical analyses of repiquete events registered from 1996 to 2018, hydraulic modeling to estimate flooded extension, and assessment of climatological characteristics during the formation of repiquetes. New hydrological insightsFloods (≥ 20 cm) produced by repiquetes in riparian crop areas between 83.00 and 88.00 m above sea level (masl) occur 1.8 times per year. However, not all elevation ranges have the same flooding risk to crops. Terrain elevations between 85.31 and 87.00 masl have a reduced flooding risk of 0.35 per year. Likewise, areas with elevations between 87.00 and 88.00 masl (43% of the total area) were not affected by repiquetes. Extreme repiquetes (study cases of 2002 and 2008) have been influenced by the increase of atmospheric moisture flux convergence and precipitation over both the northern Ucayali and Marañón basins through the six previous days. Flood impacts from the extreme event of 2002 (2008) could have reached 40% (25%) of the available area for agriculture at the initiation of the repiquete.

Long-term mercury contamination does not affect the microbial gene potential for C and N cycling in soils but enhances detoxification gene abundance.

Soil microorganisms are key transformers of mercury (Hg), a toxic and widespread pollutant. It remains uncertain, however, how long-term exposure to Hg affects crucial microbial functions, such as litter decomposition and nitrogen cycling. Here, we used a metagenomic approach to investigate the state of soil functions in an agricultural floodplain contaminated with Hg for more than 80 years. We sampled soils along a gradient of Hg contamination (high, moderate, low). Hg concentrations at the highly contaminated site (36 mg kg–1 dry soil on average) were approximately 10 times higher than at the moderately contaminated site (3 mg kg–1 dry soil) and more than 100 times higher than at the site with low contamination (0.25 mg kg–1 dry soil; corresponding to the natural background concentration in Switzerland). The analysis of the CAZy and NCyc databases showed that carbon and nitrogen cycling was not strongly affected with high Hg concentrations, although a significant change in the beta-diversity of the predicted genes was observed. The only functional classes from the CAZy database that were significantly positively overrepresented under higher Hg concentrations were genes involved in pectin degradation, and from the NCyc database dissimilatory nitrate reduction and N-fixation. When comparing between low and high Hg concentrations the genes of the EggNOG functional category of inorganic ion transport and metabolism, two genes encoding Hg transport proteins and one gene involved in heavy metal transport detoxification were among those that were highly significantly overrepresented. A look at genes specifically involved in detoxification of Hg species, such as the mer and hgc genes, showed a significant overrepresentation when Hg contamination was increased. Normalized counts of these genes revealed a dominant role for the phylum Proteobacteria. In particular, most counts for almost all mer genes were found in Betaproteobacteria. In contrast, hgc genes were most abundant in Desulfuromonadales. Overall, we conclude from this metagenomic analysis that long-term exposure to high Hg triggers shifts in the functional beta-diversity of the predicted microbial genes, but we do not see a dramatic change or breakdown in functional capabilities, but rather functional redundancy.

Floodplain agriculture can prevent the disturbance of rainforests in Amazonia

Floodplain agriculture can prevent the disturbance of rainforests in Amazonia

Organo-mercury species in a polluted agricultural flood plain: Combining speciation methods and polymerase chain reaction to investigate pathways of contamination

The analysis of organic mercury (Hg) species in polluted soils is a necessary tool to assess the environmental risk(s) of mercury in contaminated legacy sites. The artificial formation of monomethylmercury (MeHg) during soil extraction and/or analysis is a well-known limitation and is especially relevant in highly polluted areas where MeHg/Hg ratios are notoriously low. Although this has been known for almost 30 years, the thorough characterisation of artificial formation rates is rarely a part of the method development in scientific literature. Here we present the application of two separate procedures (inorganic Hg (iHg) spiking and double-spike isotope dilution analyses (DSIDA)) to determine and correct for artificial Hg methylation in MeHg-selective acid-leaching/organic solvent extraction procedure. Subsequently, we combined corrected MeHg and ethylmercury (EtHg) measurements with PCR amplification of hgcA genes to distinguish between naturally formed MeHg from primary deposited MeHg in soils from a legacy site in a Swiss mountain valley. We found the DSIDA procedure incompatible with the organomercury selective extraction method due to the quantitative removal of iHg. Methylation factors from iHg spiking were in the range of (0.0075 ± 0.0001%) and were consistent across soils and sediment matrices. Further, we suggest that MeHg was deposited and not formed in-situ in two out of three studied locations. Our line of evidence consists of 1) the concomitant detection of EtHg, 2) the elevated MeHg concentrations (up to 4.84 μg kg−1), and 3) the absence of hgcA genes at these locations. The combination of Hg speciation and methylation gene (hgcA) abundance analyses are tools suited to assess Hg pollution pathways at Hg legacy sites.

Floodplain farming and maladaptation to extreme rainfall events in northern Ghana

ABSTRACT The floodplain of the Black Volta River traverses the Ghana-Burkina Faso international border and offers considerable potential for agriculture. Yet, it is a risk-filled landscape with acute vulnerability to flooding. This paper seeks to explain why agriculture in the floodplain remains so popular when it manifestly causes more problems. Data for the paper comes from empirical fieldwork using qualitative in-depth interviews (n = 68), which were analysed using a deductive coding approach. Overall, the findings suggest that mining-induced land displacement compels farmers to engage in floodplain agriculture despite heightened vulnerability to flooding. For landless women in particular, an additional pressure is gendered responsibilities in household food provisioning, as well as subjectivities linked to norms of being good wives, mothers, and daughters-in-law. To reduce agriculture’s vulnerability to flooding, farmers often raise artificial levees on the floodplain or alter fields to drain water more quickly. The maladaptive outcomes of these practices are assessed in the paper, including rebounding vulnerability, shifting vulnerability, and destroying common pool resources. Ultimately, the paper makes two broader contributions. First, it demonstrates the importance in maladaptation analysis of paying attention to gendered subjectivities and the intersection with other social categories that can create heightened vulnerability. Second, the paper emphasizes how the causal structures of vulnerability need to form the foundation upon which maladaptation experiences are examined.

Reassessing the multiple values of lowland British floodplains

Ecosystem services provided by lowland British floodplains respectively under semi-natural conditions and converted for intensive maize production were assessed. Floodplains across lowland Britain have been extensively disconnected from river channels, depleting habitat for wildlife and other beneficial ecosystem services. Conservation measures are often regarded as costly constraints on economic and development freedoms whilst, conversely, conversion for intensive agricultural production is rewarded by markets despite many often-overlooked externalities. Maize growing has increased in Britain since the 1970s, initially for feedlot production of livestock and now increasingly for grant-aided biofuel production for anaerobic digestion. Comparative literature-based ecosystem service assessments using the RAWES (Rapid Assessment of Wetland Ecosystem Services) approach reveal that lowland British floodplains in semi-natural condition provide a wider range of provisioning services than those converted for monocultural intensive production of maize, in addition to a diversity of regulating, cultural and supporting service benefits that are lost or transformed into disservices when floodplains are converted for intensive maize growth. Benefits and disbenefits of floodplains managed under the two scenarios (semi-natural versus monocultural maize) are presented graphically as an intuitive means to support decision-makers. Monetisation of benefits would be risky, not merely due to uncertainties but as this may skew conclusions and subsequent decision-making towards maximisation of marketed or near-market services, consequently misrepresenting the diversity of values of whole socioecological floodplain systems. Management solutions protective of the societal values provided by floodplain ecosystem may include buffer zoning as a mitigation measure, but a more strategic solution may be zonation of land use based on suitability not only for crop production but recognising the full spectrum of societally beneficial ecosystem services demonstrated by RAWES assessment. A variety of drivers for a changing approach to floodplain farming – statutory, fiscal and self-beneficial – are highlighted, and are generically applicable beyond Britain with context-specific modification.

Anthropogenic Aquifer Recharge Effect on Groundwater Resources in an Agricultural Floodplain in Northeastern Tunisia: Insights from Geochemical Tracers and Geophysical Methods

Anthropogenic Aquifer Recharge Effect on Groundwater Resources in an Agricultural Floodplain in Northeastern Tunisia: Insights from Geochemical Tracers and Geophysical Methods

Pollution Pathways of Mercury and Organic Mercury Species in a Contaminated Agricultural Flood Plain. The Need for a Complete Toolbox

Pollution Pathways of Mercury and Organic Mercury Species in a Contaminated Agricultural Flood Plain. The Need for a Complete Toolbox

НАВОДНЕНИЯ В ЗАПАДНОЙ СИБИРИ В КОНТЕКСТЕ ПРИРОДНО-ХОЗЯЙСТВЕННЫХ ВЗАИМОСВЯЗЕЙ (XVIII — НАЧАЛО XX в.)

In terms of scale and devastating consequences, floods are the most dangerous thing among natural disasters. The article is an attempt to assess their impact on the settlements and economic development in the Ob-Irtysh river system within the West Siberian region in the 18th — early 20th centuries. Floods which had high waters were associated with spring floods, but the water could not subside until the fall or even before the ice break. There were also catastrophic ones with a very high level. In addition, some complications such as long high-water cycles accrued at the time when the level and frequency of flooding increased. During severe and catastrophic floods settlements and agricultural land were flooded, livestock died, houses and outbuildings were destroyed or rendered unusable, and communication routes were interrupted for a long time. In the north of the region (Lower Ob region) during catastrophic floods, fishing trade was almost stopped and the opportunities for cattle breeding in the flooded floodplain were sharply reduced. Floodplain agriculture fell into decay during high-water cycles in the southern boreal forest area. The population of coastal areas tried to protect themselves from flooding with storage dams, but they were not built everywhere and often could not withstand the pressure of water. The only effective means of flood defense was relocation to high river banks. Therefore, the floods in 1912 and 1914 years provoked the relocation of the Irtysh River low-cost residents of the Tobolsk province. The authorities facilitated this relocation. Assistance was provided to flood victims, even though not so often. In these conditions, the population often had to rely only on themselves and God’s help. Thus, for example, in the city of Berezov the cult of St. Epiphanius was formed. On his Memorial Day people asked the higher forces for help in eliminating the consequences of the flood. But the most effective tool in combating floods was folk natural science knowledge. Over the long history of life on the river, the Russian population has developed omens, which helped them to judge the level of the upcoming flood. Among the enlightened part of the local population, there were ideas about the cyclical nature of catastrophic floods.

The Economic and Ecological Contexts of Urbanization in the Great Hungarian Plain during the Eighteenth and Nineteenth Centuries

There is abundant research on the history of urbanization in the Carpathian Basin with a special focus on the history of urbanization in the Great Hungarian Plain. Over the past years, there have been investigations concerning climate and historical ecology issues, as well as economic and social history, the results of which enable us to obtain an overview of the complex processes in the eighteenth and nineteenth centuries.It has been confirmed that prior to the Industrial Age (1850), climate change had made a profound impact on the conversion of the settlement network in the terrain and on the expansion of livestock farming. The climate in the seventeenth century seems to have been cooler and more humid, thus in the Great Hungarian Plain there were large areas covered with water. This significantly restricted the possibilities of crop cultivation as well as population growth. The warming-up period in the eighteenth century resulted in the shrinking of areas covered in water, the transition to flood plain farming and the extension of plough land crop cultivation, ultimately leading to population growth. There is evidence that by the turn of the eighteenth-nineteenth centuries, grain trade in the Carpathian Basin had been integrated into the Central European continental crop trading system, however, livestock farming was unique to the Great Hungarian Plain. From the mid-nineteenth century, due to the construction of the railway system in the Great Hungarian Plain, which revolutionized cargo transport, plus due to river regulations and drainage works, the economic structure of the area saw profound changes. In the meanwhile, the population and labor force supply were also increasing at a rapid rate. Marshlands and meadows were replaced by arable land and an increasingly growing crop production, which provided the foundations for the grain trade. Thus, new market centers emerged in the Great Hungarian Plain. Between 1828 and 1925, the number of market centers went up by 293, which represents an elevenfold rise. The growing density of the market center system significantly defined not only various aspects of urbanization, but also the general modernization of the Great Hungarian Plain.The purpose of my research is to analyze how changes in the climate influenced the settlement network, and the social and economic profile of the Great Hungarian Plain in the period concerned. Why was the favorable picture of a dynamically improving and modernizing Great Hungarian Plain at the turn of the nineteenth and twentieth centuries conceptualized by the public as an underdeveloped area characterized by a series of economic and social tensions? How do all these factors contribute to the revision of the emerging historiographic picture of the economic and social consequences of the Trianon Peace Treaty?

What drives clearing of old-growth forest over secondary forests in tropical shifting cultivation systems? Evidence from the Peruvian Amazon

A key issue in understanding tropical forest disturbance is what drives farmers practicing customary shifting cultivation to clear crop fields in old-growth forest over secondary forest fallows. These farmers typically hold a stock of secondary forest fallows that can be used for cropping in rotation, built up over time in part through initial clearing of old-growth forest. In this paper we examine the most recent field cleared by 2046 indigenous and folk peasant households in 138 communities along three major rivers of the Peruvian Amazon to identify the factors that influence their choice of field location (upland or lowland forests) and type of forest cleared (old-growth or secondary). Data are drawn from a large-scale household and community surveys and remote sensing analysis of Landsat and ArcGIS Worldview imagery. We find that rates of old-growth forest clearing are low and that such land quickly returns to secondary forest cover: about 31% of households cleared forest on the upland (terra firme) but only 8% of households cleared upland old-growth forest. Regression modeling results identify the contextual, historical and household factors that influence the choice to clear upland forest (old-growth or secondary). Access to lowland for floodplain agriculture is associated with lower rates of old-growth forest clearing and higher educational attainment of household heads with increased clearing. Analysis of household land portfolios points to the importance of the size of land holdings, the degree of upland orientation, and the number and age of fallows held at the time of the forest clearing decision in clearing old-growth forest on the upland. Measures to reduce old-growth forest loss around Amazonian communities are discussed.

Improving waterbird monitoring and conservation in the Sahel using remote sensing: a case study with the International Waterbird Census in Sudan

In several regions of the world, the remoteness of potential bird hotspots and lack of trained observers have often prevented countries from effectively designing proper monitoring schemes at a national scale. For many countries, it is not known whether certain bird strongholds have been missed that should be included for more complete censuses. Such gaps at national scales, sometimes large, may be detrimental for global monitoring schemes. To address this, we used the irregular participation of Sudan to the International Waterbird Census (IWC) as a case study. We designed and tested a method based on remote‐sensing data of the country’s lowlands to detect open water bodies in order to develop predictive models of the potential distribution of waterbird abundance and diversity. To identify open water bodies and their flooding duration, we used a Modified Normalized Difference Water Index (MNDWI) derived from Landsat 8 data. Field ornithological surveys were then used as ground‐truth data to estimate the method’s accuracy. The statistical results (overall accuracy = 0.972; Kappa index = 0.93) confirmed its effectiveness. Remotely sensed water bodies and additional environmental covariates were then used to build simple habitat models of the distribution of waterbird abundance and diversity based on IWC field survey data. Of the 3119 remotely sensed clusters of open water bodies, three were predicted to host more than 10 000 waterbirds, 89 more than 1000 waterbirds and five more than 30 waterbird species. Located mainly in the southern agricultural floodplains along the main rivers, these predicted waterbird strongholds are therefore recommended for inclusion in the next IWC survey in Sudan. Our findings indicate that using remote sensing to identify open water bodies combined with simple statistical modelling is likely to be a cost‐effective solution to improve IWC sampling and to enhance both waterbird and wetland monitoring in vast under‐surveyed regions.

Farm to Fish: Lessons from a Multi-Year Study on Agricultural Floodplain Habitat

Large areas of California’s historic floodplain have been separated from adjacent river channels by levee construction, allowing the development of an extensive agricultural industry. Based on successful partnerships between agriculture and conservation groups to support migrating waterfowl, we examined whether seasonally flooded rice fields could be modified to provide off-channel rearing habitat for juvenile Chinook Salmon Oncorhynchus tshawytscha. During winter and spring of 2012-2017, we conducted a series of experiments in Yolo Bypass and other regions of California’s Central Valley using hatchery Chinook Salmon as a surrogate for wild Chinook Salmon, the management target for our project. Overall, we found that seasonally flooded fields are highly productive, resulting in significantly higher levels of zooplankton and high Chinook Salmon growth rates as compared to the adjacent Sacramento River. We found similar results for multiple geographical areas in the Central Valley, and in different cover types, such as non-rice crops and fallow areas. Although field substrate type did not detectably affect fish growth and survival, connectivity with upstream and downstream areas appeared to drive fish occupancy, because rearing young salmon were generally attracted to inflow in the fields, and not all of the fish successfully emigrated off the fields without efficient drainage. In general, we faced numerous logistic and environmental challenges to complete our research. For example, periodic unmanaged floods in the Yolo Bypass made it difficult to schedule and complete experiments. During severe drought conditions, we found that managed agricultural habitats produced low and variable salmon survival results, likely because of periodically high temperatures and concentrated avian predation. In addition, our project required substantial landowner time and effort to install and maintain experimental fields. Recent and future infrastructure improvements in Yolo Bypass could substantially improve options for experimental work and broaden efforts to enhance salmon habitat.

Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain.

Similar to many large river valleys globally, the Sacramento River Valley has been extensively drained and leveed, hydrologically divorcing river channels from most floodplains. Today, the former floodplain is extensively managed for agriculture. Lack of access to inundated floodplains is recognized as a significant contributing factor in the decline of native Chinook Salmon (Oncorhynchus tshawytscha). We observed differences in salmon growth rate, invertebrate density, and carbon source in food webs from three aquatic habitat types—leveed river channels, perennial drainage canals in the floodplain, and agricultural floodplain wetlands. Over 23 days (17 February to 11 March, 2016) food web structure and juvenile Chinook Salmon growth rates were studied within the three aquatic habitat types. Zooplankton densities on the floodplain wetland were 53x more abundant, on average, than in the river. Juvenile Chinook Salmon raised on the floodplain wetland grew at 0.92 mm/day, 5x faster than fish raised in the adjacent river habitat (0.18 mm/day). Two aquatic-ecosystem modeling methods were used to partition the sources of carbon (detrital or photosynthetic) within the different habitats. Both modeling approaches found that carbon in the floodplain wetland food web was sourced primarily from detrital sources through heterotrophic pathways, while carbon in the river was primarily photosynthetic and sourced from in situ autotrophic production. Hydrologic conditions typifying the ephemerally inundated floodplain—shallower depths, warmer water, longer water residence times and predominantly detrital carbon sources compared to deeper, colder, swifter water and a predominantly algal-based carbon source in the adjacent river channel—appear to facilitate the dramatically higher rates of food web production observed in the floodplain. These results suggest that hydrologic patterns associated with seasonal flooding facilitate river food webs to access floodplain carbon sources that contribute to highly productive heterotrophic energy pathways important to the production of fisheries resources.