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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.

Monthly to seasonal streamflow forecasts provide useful information for a range of water resource management and planning applications. This work focuses on improving such forecasts by considering the following two aspects: (1) state updating to force the models to match observations from the start of the forecast period, and (2) selection of a shorter calibration period that is more representative of the forecast period, compared to a longer calibration period traditionally used. The analysis is undertaken in the context of using streamflow forecasts for environmental flow water management of an open channel drainage network in southern Australia. Forecasts of monthly streamflow are obtained using a conceptual rainfall–runoff model combined with a post-processor error model for uncertainty analysis. This model set-up is applied to two catchments, one with stronger evidence of non-stationarity than the other. A range of metrics are used to assess different aspects of predictive performance, including reliability, sharpness, bias and accuracy. The results indicate that, for most scenarios and metrics, state updating improves predictive performance for both observed rainfall and forecast rainfall sources. Using the shorter calibration period also improves predictive performance, particularly for the catchment with stronger evidence of non-stationarity. The results highlight that a traditional approach of using a long calibration period can degrade predictive performance when there is evidence of non-stationarity. The techniques presented can form the basis for operational monthly streamflow forecasting systems and provide support for environmental decision-making.

Drainage ditches play a key role in the conservation of fragmented landscapes by providing refuge sites and secondary habitats for many terrestrial and aquatic organisms across various taxa. Species richness of ditches can exceed that of adjacent natural habitats, but here, we looked further and assessed the role of drainage ditches in shaping the community structure of true bugs aiming to better estimate ditches’ conservation value from the point of their species and trait composition. We tested the effects of the ditch substrate (saline, sandy or fen), landscape matrix (agrarian or grassland) and vegetation (species richness of all plants and invasive plants, and abundance of woody plants) on the true bug communities of 60 drainage ditches in the lowland of East-Central Europe. We found that substrate and landscape matrix contributed the most in determining true bug communities. Based on species composition, different substrates and landscape matrix types had distinct communities, but the trait composition showed differentiation according to the landscape matrix in saline habitats only. The trait composition in true bug communities was more diverse in grassland ditches than in agrarian ones, which hosted more habitat generalists associated with invasive vegetation. We concluded that a pronounced gradient in habitat stress, originating in substrate salinity and aridity, causes the differentiation of the true bug communities based on their trait composition. Additionally, intense habitat stress increases the number of habitat specialists and the conservation value of a drainage ditch.

Agricultural drainage ditches are ubiquitous features in lowland agricultural landscapes, built primarily to facilitate land drainage, irrigate agricultural crops and alleviate flood risk. Most drainage ditches are considered artificial waterbodies and are not typically included in routine monitoring programmes, and as a result the faunal and floral communities they support are poorly quantified. This paper characterises the aquatic macroinvertebrate diversity (alpha, beta and gamma) of agricultural drainage ditches managed by an internal drainage board in Lincolnshire, UK. The drainage ditches support very diverse macroinvertebrate communities at both the site (alpha diversity) and landscape scale (gamma diversity) with the main arterial drainage ditches supporting greater numbers of taxa when compared to smaller side ditches. Examination of the between site community heterogeneity (beta diversity) indicated that differences among ditches were high spatially and temporally. The results illustrate that both main arterial and side ditches make a unique contribution to aquatic biodiversity of the agricultural landscape. Given the need to maintain drainage ditches to support agriculture and flood defence measures, we advocate the application of principles from ‘reconciliation ecology’ to inform the future management and conservation of drainage ditches.

In the city of Malang, which is a highland area, there are still floods, including Blimbing and Lowokwaru sub-districts. One of the causal factors is the change of undeveloped areas becoming relatively large built-up areas in the Upper Brantas sub-watershed, from initially 20.5% in 2000 to 69.6% 20 years later. This change also impacts the transformation of irrigation canals that once irrigated rice fields, causing them to shift their function into drainage channels that carry runoff water toward natural channels (natural drainage). Consequently, the existing canal conditions cannot accommodate the runoff water. The research employed an approach that involved analyzing floodwater management models using the Storm Water Management Model (SWMM 5.1) and surveying existing canal data. The analysis results revealed that, within the studied areas of Blimbing Village and the Blimbing Catchment Area, 10 out of the existing 170 drainage channels were incapable of handling the discharge associated with rainfall intensities designed for return periods of 5 years (112.48 mm/day) and ten years (117.09 mm/day). In the Lowokwaru Catchment Area, it was evident that 18 out of the 216 existing canals experienced overflow events with designed flood discharge for 5-year and 10-year periods.

Data from the Environmental Health Risk Assessment (EHRA) study in 2012 stated that 52% of inundation in Banjarmasin City was caused by a problematic drainage system, the causes of which included siltation of the canals and the large number of weeds growing around the drainage canals, which would interfere with the function of the drainage canals. The data used are road canal cross-sectional dimensions, topographical data, canal alignment data, and land use data in North Banjarmasin Sub District. The calculation analysis method uses the Mononobe method. The results of these calculations will later be used for modeling which are indicated to exceed the water capacity, of course also by adding topographical parameters, land use, and canal alignment. Meanwhile, the planned discharge data from the results of the calculated rainfall and the measuring data of the channel cross-sectional dimensions are used for detailed modeling of the channel cross-section using HecRas. The condition of drainage channels is over-capacity, influenced by the presence of several channels covered with bushes and concrete, the amount of sediment that has not been dredged, the absence of an adequate catchment area system due to the characteristics of the soil in the form of peat soil.

In Europe, large rivers have been greatly impacted by engineering and hydraulic works. The Upper Rhine channelization has notably led to a disconnection between the main channel and its floodplain and side channels. Between 1998 and 2006, unprecedented restoration projects led to the reconnection of nine Rhine side channels to the main channel or the Rhine Drainage Canal. The structures of recolonizing macroinvertebrate communities observed in the restored side channels, either in 2009 or 2010, were compared to the ones of three reference side channels. The aims of the study were (i) to analyze the recolonizing macroinvertebrate communities and (ii) to identify the drivers of the community structure. The restored side channels exhibited macroinvertebrate community structures similar to those of the reference side channels. These communities were characterized by a high abundance of nonnative and invasive taxa and a structure not linked to either the time since restoration or the water and sediment chemistry. Significant correlations existed between the macroinvertebrate community structures and the mosaics of habitats, driven by the variations in side channel morphometry and discharge. Therefore, the diversity of habitat characteristics of the side channels might help conserve and increase macroinvertebrate biodiversity at the floodplain scale.

Water bodies play a very important role in maintaining and restoring the ecological balance, but they are one of the most threatened habitats in the world. Anthropogenic intervention is changing the regimes of wetlands almost everywhere particularly in the developing countries. Gorakhpur District is dotted with many big and small flood plain–related water bodies like rivers, streams, tanks, dead arms, oxbow lakes, etc. Some of these water bodies are worst affected and are degraded by encroachment for agriculture and other economic and developmental activities. Channel migration, aggravated by human intervention, on alluvial plain is also very frequent, which has direct impact on the nature of water bodies and land use transformations of the region. In this paper, the authors have made an attempt to (a) bring current geographical and historical background of water bodies/wetlands for the district. It aims to assess long-term (1917–2018) and short-term (pre- and post-monsoon) changes in the water bodies of Gorakhpur District; (b) provide changes in the regime of water bodies/wetlands and their conversion to different types of land use/land cover classes due to human intervention and due to annual rainy season, which inundates a large extent of the area every year; (C) assess the channel characteristics and morphometric analysis of main rivers of the region during the last hundred years. Remote sensing and Geographical Information System (GIS) have been used to prepare the inventory and to perform change detection, using land use/land cover maps. The floodplain areas of water bodies have almost changed their morphological characters due to encroachment by the nearby areas. Canals, drainage channels, and lakes are the most affected water bodies in the region, which have recorded − 65.38% and 43.37% loss in their area. Even permanent rivers have recorded a decrease of − 16.96% in the area. As per the seasonal change, agriculture land suffered the greatest conversion (18.33%) due to floodwater inundation. The study provides a platform to planners to chalk out their policies and also for monitoring the water bodies. Furthermore, analysis on channel migration will help predict the future course of the main rivers.

Elevated intraocular pressure (IOP) appears to have a broader impact on increased resistance to aqueous humor (AH) outflow through the conventional aqueous outflow system (AOS). However, it is still unknown how AH drainage resistance is produced or why it becomes increased in glaucoma. It is hard to accurately obtain hydrodynamic parameters of AH within the trabecular meshwork (TM) outflow pathway tissues based on current technology. In this study, we reconstructed the rat AOS model with high-resolution two-photon imaging, and simulated the AH outflow process. The resolution of the two-photon imaging system can be up to 0.5 μm for imaging the AOS tissues. Quite a few morphological parameters of rat TM in conditions of normal and elevated IOP were determined using the experiment integrated with the simulation method. We determined that the TM thickness is 49.51 ± 6.07 μm with an IOP of 5.32 kPa, which significantly differed from the TM thickness of 66.4 ± 5.14 μm in the normal IOP group. Furthermore, 3D reconstruction of local aqueous drainage channels from two-photon microscopy images revealed detailed structures of the AOS and permitted the identification of 3D relationships of Schlemm’s canal, collector channel, and trabecular drainage channels. An algorithm of finite element micro-modeling of the rat TM outflow pathways reveals the importance of TM for mechanical performance, with the potential to assist clinical therapies for glaucoma that seek to steer clear of an abnormal TM. Graphical abstract

A study was made to determine the erosion problem and determine the amount of suspended sediment transport in the drainage channels of the Harran Plain by conducting periodic suspended sediment sampling and discharge measurements in the field between 1997 and 2017. When irrigation in the Harran Plain started in 1990, the production of the agricultural goods quadrupled within a few years. Unfortunately, excessive amounts of irrigation water supplied to irrigate crops also led to the erosion of the soil in the fields by surface runoff. Furthermore, the mixture of clay, silt, and fine sand in the topsoil from certain areas accumulated in the tertiary and secondary drainage systems and reduced the effectiveness of the drainage system. Analysis of the suspended sediment measurements between 1997 and 2017 showed that the yearly averaged sediment transported to Syria by the main drainage canal of the Harran Plain varied between 128 ton.day−1 to 1268 ton.day−1, and the average of the 21-year measurement is about 682 ton.day−1. The logarithmic plot of the suspended sediment rating curve showed that as the discharge of the Cullap Creek increases, the sediment transport rate also increases linearly. It means excess furrow irrigation could cause substantial topsoil loss. Sediment erosion resulting from rainfall events in the Harran Plain is also computed using Revised Universal Soil Loss Equation (RUSLE). The results showed that rainfall erosion from the Harran Plain is 131.5 ton.day−1. A comparison of this value with the 21-year value of average sediment erosion by irrigation shows that approximately 20% of sediment erosion from the Harran Plain was caused by rainfall events, and the remaining 80% was caused by excess irrigation water in the area. A 2D numerical model was constructed with MIKE 21 software applying Van Rijn Method to calculate suspended sediment load due to irrigation, and it allowed to calculate the load with a 6.47% error. Grouping the irrigated and non-irrigated periods and applying independent t test, a statistical approach constituted and resulted in 79.2% of suspended sediment load is caused by irrigation. The numerical model and statistical analysis supported the findings of field data and RUSLE Model results. The study showed that the main reason of the topsoil loss in the Harran Plain is the excess furrow irrigation.