Drainage Ditches Research Articles

Drainage Ditch Cleaning Has No Impact on the Carbon and Greenhouse Gas Balances in a Recent Forest Clear-Cut in Boreal Sweden

Ditch cleaning (DC) is increasingly applied to facilitate forest regeneration following clear-cutting in Fennoscandinavia. However, its impact on the ecosystem carbon and greenhouse gas (GHG) balances is poorly understood. We conducted chamber measurements to assess the initial DC effects on carbon dioxide (CO2) and methane (CH4) fluxes in a recent forest clear-cut on wet mineral soil in boreal Sweden. Measurements were conducted in two adjacent areas over two pre-treatments (2018/19) and two years (2020/21) after conducting DC in one area. We further assessed the spatial variation of fluxes at three distances (4, 20, 40 m) from ditches. We found that DC lowered the water table level by 12 ± 2 cm (mean ± standard error) and topsoil moisture by 0.12 ± 0.01 m3 m−3. DC had a limited initial effect on the net CO2 exchange and its component fluxes. CH4 emissions were low during the dry pre-treatment years but increased particularly in the control area during the wet years of 2020/21. Distance to ditch had no consistent effects on CO2 and CH4 fluxes. Model extrapolations suggest that annual carbon emissions decreased over the four years from 6.7 ± 1.4 to 1.6 ± 1.6 t-C ha−1 year−1, without treatment differences. Annual CH4 emissions contributed <2.5% to the carbon balance but constituted 39% of the GHG balance in the control area during 2021. Overall, our study suggests that DC modified the internal carbon cycling but without significant impact on the carbon and GHG balances.

Amphibian-Friendly Water Drainages for Agricultural Landscapes, Based on Multiple Species Surveys and Behavioural Trials for Pelophylax nigromaculatus

Amphibians are the most threatened vertebrate group on earth, and one of the reasons for their decline is habitat loss. While some populations have persisted in agricultural wetlands such as rice paddies, the current anthropisation of landscapes is dealing a new blow to the survival of these species. In rice paddies, the new threats are especially visible through the increased channelization of water bodies with increasingly efficient drainage ditches, which become deadly traps. We first conducted surveys over three years to determine the use of ditches by frog species for natural versus concrete ditches, and thus relate to habitat adequacy as well as the probability of becoming trapped in concrete ditches. We then set up four types of experimental arena for escape trials. Experiments were replicated for the Black-spotted pond frog (Pelophylax nigromaculatus), as a proxy for other species abundant in rice paddies in the Republic of Korea. We determined that a slope of at least 70 degrees, with engraved patterns, was the only set-up from which frogs managed to escape. We recommend the implementation of this type of device in areas where a high concentration of animals is trapped, before phasing out the ancient design and relying on amphibian-friendly drainage ditches as they also support higher amphibian biodiversity.

Citizen Science Helps Uncover the Secrets to a Bat-Friendly Swimming Pool in an Urban Environment

For urban environments to support bat communities, resources need to be readily available. For example, bats typically use urban water sources such as drainage ditches and ponds; however, these sources can be ephemeral. During these periods, bats have utilized residential swimming pools, although they only appear to drink at pools when access to more natural equivalents are limited. This posed the question “can we make residential swimming pools friendlier for a diversity of bat species?” Using citizen science to determine which pool characteristics influenced bat activity, we distributed a questionnaire to residents in a suburban neighborhood in Fort Worth, TX, United States. It focused on observations of bat activity and the features of the pools and immediate surroundings. We distributed the questionnaire through social media, local presentations, and by mail throughout 2019 and 2020. We then used classification trees to determine which characteristics in combination influenced bat activity at the pools. We generated three different trees for bats observed (1) flying around the property and backyard, (2) above the swimming pool, and (3) drinking at the pool. We found that more bats were observed at unlit pools without bush or shrub borders. Furthermore, among pools with borders, activity was lowest at pools with textured interiors and ≥6 trees visible. The presence of features, such as fountains, then contributed to a reduction in bat observations in backyards and the presence of pets appeared to further reduce activity specifically over the pools. Where bats were observed drinking, this activity was reported the least at pools with bush or shrub borders, textured interiors, and trees <5 m and >10 m from the edge of the pools. Our study revealed that certain characteristics of residential swimming pools encouraged bat activity, while others discouraged them. Thus, it may be possible to make swimming pools more bat-friendly. For example, turning lights off in the evening when backyards are not in use and reducing clutter around pools could have an immediate positive impact on local bat populations. The implementation of such recommendations could improve urban habitats for bats overall and alleviate some of the negative implications of continued urbanization.

Lateral sediment connectivity of landslides occurred under a heavy rainstorm and its influence on sediment yield of slope-channel cascade on the Loess Plateau

The rate at which sediment enters the channel network in the landscape reflects lateral sediment connectivity of the landscape and has significant implications on the hydrological processes in a catchment. The main objective of this research was to quantify the lateral sediment connectivity of landslides and explore their relationship to the sediment yield of slope-channel cascades. Combining fieldwork and unmanned aerial vehicle techniques, we mapped all landslide inventories and calculated the amount of soil erosion. We proposed a new lateral sediment connectivity index (LCI), which takes into account landslide area density, landslide connectivity characteristics, and landslide potential transport distance, to explore whether landslides that occurred under heavy rainstorms affect the sediment yield in slope-channel cascades through legacy effects. Results showed that the area of landslides ranged from 0.2 m2 to 1100.07 m2, and the soil erosion amount of landslides ranged from 0.21 t to 1690.81 t during the rainstorm that occurred on 4 August. 2020 with a cumulative rainfall of 216.4 mm. The LCI of landslides was more closely related to the sediment yield of slope-channel cascades after the rainstorm. It was indicated that LCI is a good index to quantify the effect of lateral sediment connectivity of landslides on sediment yield in the catchment and that landslides generated by heavy rainstorms have long-term impacts on sediment transport processes in the slope-channel cascades of the catchment. Regarding slope management, we propose to protect gully slopes by reducing lateral sediment connectivity between upslope areas and gully slopes and to protect terrace slopes by constructing boundary dikes and drainage ditches to reduce slope collapse under heavy rainstorms.

Chemical Evolution Process and Quality Assessment of Seepage Groundwater in Tunnel Crossing Gas-Bearing Coal Seams

The chemical characteristics of groundwater in the gas coal seam section of the tunnel have rich geological significance. To study the chemical evolution process and controlling factors of groundwater in the gas-bearing coal seam section of the tunnel, and the influence of tunnel coal removal on the groundwater quality, field investigations and laboratory experiments were carried out on the groundwater in the coal measure strata and the high-gaseous section and surrounding aquifers. Through hydrochemical analysis, correlation analysis, hydrochemical simulation, and other methods, the chemical origin of groundwater in coal measure strata and other aquifers was revealed. The water quality of groundwater was analyzed by water quality index (WQI), sodium adsorption rate (SAR), percentage of soluble sodium (Na+%), and participation of sodium carbonate (RSC). The results show that the water samples of each aquifer are weakly alkaline. Influenced by formation lithology and mineral redox reactions, the genesis of coal formation water is more complex than that of natural karst groundwater. The water chemistry characteristics show obvious differences among aquifer groups, with low correlation of HCO3-, Ca2+, and Mg2+. The central drainage ditch is dominated by dolomite dissolution, and the sloping shaft side ditch is dominated by calcite dissolution, and ion exchange effects are prevalent in different water sources. In terms of irrigation water quality, the permeability index (PI), magnesium hazard (MH), and Kelly index (KI) calculations show that 45.8% of the water samples are in the “unsuitable” condition. This study helps to fully understand the quality of coal seam water in tunnels and can provide a reference for groundwater utilization.

Nitrogen migration paths and source areas at different snowmelt periods in a seasonal freezing agricultural watershed

Study regionHeidingzi, a typical seasonal freezing agricultural watershed in northeastern China. Study focusThis study’s objectives were to: (1) confirm whether nitrogen source areas and migration paths have changed with the melting of snow and frozen soil; (2) find an effective way to recognize the change points and separate nitrogen export processes to different periods during snowmelt; and (3) identify the source areas, migration paths, and critical influencing factors of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) in river water during these snowmelt periods. New hydrological insights for the regionThe nitrogen export process during snowmelt can be divided into two stages according to the relationship between δ18O and nitrogen concentration. Nitrogen concentration had a linear relationship with δ18O during early snowmelt periods, while they varied within a small range during the late stages. Paddy field area proportion (PFP), Rural area proportion (RAP), Average Slope (AS), Slope area proportion < 2° (SAP < 2°), and SAP (6–15°) greatly affected water discharge, nitrogen concentration, and yield. Lower slope areas along the river expended water and nitrogen via soil saturation and depression detention. The NH4+-N and NO3−-N in these areas were flushed into rivers by water from steeper areas (slope > 6°). Abundant nitrogen reserves near the river compensated for the negative impact of water shortage on nitrogen yield during early snowmelt periods. Water and nitrogen in rural areas came mainly from snow-scattered areas during early snowmelt periods, and from frozen domestic sewage or refrozen snowmelt in drainage ditches during late snowmelt periods.

Lost in the North Sea-Geophysical and geoarchaeological prospection of the Rungholt medieval dyke system (North Frisia, Germany).

We performed geophysical and geoarchaeological investigations in the Wadden Sea off North Frisia (Schleswig-Holstein, Germany) to map the remains and to determine the state of preservation of the medieval settlement of Rungholt, especially its southern dyke segment, called the Niedam dyke. Based on archaeological finds and historical maps, Rungholt is assumed to be located in the wadden sea area around the island Hallig Südfall. During medieval and early modern times, extreme storm events caused major land losses, turning cultivated marshland into tidal flats. Especially the 1st Grote Mandrenke (or St. Marcellus' flood), an extreme storm surge event in 1362 AD, is addressed as the major event that flooded and destroyed most of the Rungholt cultural landscape. Cultural traces like remains of dykes, drainage ditches, tidal gates, dwelling mounds or even plough marks were randomly surveyed and mapped in the tidal flats by several authors at the beginning of the 20th century. Due to the tidal flat dynamics with frequently shifting tidal creeks and sand bars, the distribution of cultural remains visible at the surface is rapidly changing, making it hard to create a comprehensive map of the cultural landscape by surveying. Today, the Niedam dyke area is fully covered by tidal flat sediments, depriving any remains from further archaeological investigation. Since little is known about the precise location or state of preservation of these remains, our investigation aimed at the rediscovery of the medieval dyke system and associated structure with modern and accurate geophysical, geodetical and geoarchaeological methods. Magnetic gradiometry revealed a large part of the medieval dyke, confirming two tidal gates and several terps connected inland with the dyke, providing a detailed example of a Frisian medieval dyke system. Based on our results, the so far inaccurate and incomplete maps of this part of Rungholt can now be specified and completed. Beyond that, seismic reflection profiles give a first depth resolving insight in the remains of the dyke system, revealing a severe threat to the medieval remains by erosion. The site is exemplary for the entire North Frisian coast, that was influenced by multiple flood events in the middle ages to modern times.

Simulation and Experiment of Spiral Soil Separation Mechanism of Compound Planter Based on Discrete Element Method (DEM)

In order to solve the problems of blocking the drainage ditch and reducing the soil flatness caused by soil accumulation when using compound planter with plowshare to ditch, a spiral soil separation mechanism (SSSM) is designed. The SSSM is analyzed. In order to obtain the optimal parameters of the SSSM, based on the discrete element method, the multifactor test is carried out with the embedded depth, pitch, and rotation speed of the spiral blade as the test factors and the soil separation distance and uniformity as the evaluation index. The optimal parameters are the embedded depth 49 mm, pitch 331 mm, and rotation speed of the spiral blade 318 r min−1. The field experiment is carried out with these parameters, with soil separation distance 900 mm and standard deviation of soil height 7.8 mm, which is consistent with the simulation results. No blockage of drainage ditch was found, which shows that this device can effectively solve the problem. This study can provide a reference for the design of soil separation equipment using spiral soil separation device.

Effects of Drainage Water Management in a Corn–Soy Rotation on Soil N2O and CH4 Fluxes

Drainage water management (DWM), also known as controlled drainage, is a best management practice (BMP) deployed on drainage ditches with demonstrated success at reducing dissolved nitrogen export from agricultural fields. By slowing discharge from agricultural ditches, subsequent anaerobic soil conditions provide an environment for nitrate to be reduced via denitrification. Despite this success, incomplete denitrification might increase nitrous oxide (N2O) emissions and more reducing conditions might increase methanogenesis, resulting in increased methane (CH4) emissions. These two gases, N2O and CH4, are potent greenhouse gases (GHG) and N2O also depletes stratospheric ozone. This potential pollution swapping of nitrate reduction for GHG production could negatively impact the desirability of this BMP. We conducted three years of static chamber measurements of GHG emissions from the soil surface in farm plots with and without DWM in a corn–soybean rotation on the Delmarva Peninsula. We found that DWM raised the water table at the drainage ditch edge, but had no statistically significant effect on water-filled pore space in the field soil surface. Nor did we find a significant effect of DWM on GHG emissions. These findings are encouraging and suggest that, at least for this farm site, DWM can be used to remove nitrate without a significant tradeoff of increased GHG emissions.

Macrophyte communities as indicators of the ecological status of drainage canals and regulated rivers (Eastern Poland)

Macrophytes are one of the biological elements for assessing the ecological status. Macrophyte communities were studied in six artificial (drainage canal and ditches) or modified watercourses (regulated rivers). In order to assess the ecological status of the watercourses, studies were carried out with the use of the Macrophyte Index for Rivers (MIR) proposed in the Water Framework Directive. Macrophyte communities were mainly represented by helophytes (12 species in total), and the highest percentage area cover (50–75% of the site) was observed for pleustophytes (Lemna spp.). Macrophytes communities were affected by the gradients of hydromorphological (canal modification, flow type, and shading) and parameters water quality (nutrients and water transparency). The relationships were highly species-specific. In accordance with the MIR values, the ecosystems were classified as having poor (drainage canal), moderate (regulated rivers), or good (drainage ditches) ecological status.

Assessing the Influences of Land Use Change on Groundwater Hydrochemistry in an Oasis-Desert Region of Central Asia

Land use change greatly affects groundwater hydrochemical cycling and thereby food and ecosystem security in arid regions. Spatiotemporal distribution of groundwater hydrochemistry is vital to understand groundwater water-salt migration processes in the context of land use change, while it is not well known in the oasis-desert region of arid inland basins. Here, to investigate the influences of land use change on groundwater hydrochemistry and suggest sustainable management, 67 water samples were obtained in the Luntai Oasis, a typical oasis desert of Central Asia. Stable isotopes and chemical components of samples were analyzed. Piper and Gibbs plots were used to elaborate the chemical type and major mechanisms controlling water chemistry, respectively. The results showed that cultivated land area has markedly expanded in the Luntai Oasis over the last 20 years (increasing by 121.8%). Groundwater seasonal dynamics and groundwater–surface water interaction were altered dramatically by farmland expansion and groundwater exploitation. Specifically, the spatial heterogeneity and seasonal variability of groundwater hydrochemistry were significant. Compared with the desert area, the δ18O and TDS of river water and shallow groundwater in the oasis cropland exhibited lower values but greater seasonal variation. Higher TDS was observed in autumn for river water, and in spring for shallow groundwater. The chemical evolution of phreatic water was mainly controlled by the evaporation-crystallization process and rock dominance, with a chemical type of Cl-SO4-Na-Mg. Significant spatiotemporal heterogeneity of groundwater hydrochemistry demonstrated the influence of climatic, hydrogeological, land use, and anthropogenic conditions. Groundwater overexploitation would cause phreatic water leakage into confined water, promoting groundwater quality deterioration due to fresh saltwater mixing. Improving agricultural drainage ditches in conjunction with restricting farmland expansion and groundwater extraction is an effective way to alleviate groundwater environment deterioration and maintain oasis-desert ecosystems in arid regions.

Nitrogen Transport/Deposition from Paddy Ecosystem and Potential Pollution Risk Period in Southwest China

Nitrogen (N) losses through runoff from cropland and atmospheric deposition contributed by agricultural NH3 volatilization are important contributors to lake eutrophication and receive wide attention. Studies on the N runoff and atmospheric N deposition from the paddy ecosystem and how the agriculture-derived N deposition was related to NH3 volatilization were conducted in the paddy ecosystem in the Erhai Lake Watershed in southwest China. The critical period (CP) with a relatively high total N (TN) and NH4+-N deposition occurred in the fertilization period and continued one week after the completion of fertilizer application, and the CP period for N loss through surface runoff was one week longer than that for deposition. Especially, the mean depositions of NH4+-N in the CP period were substantially higher than those in the subsequent period (p &lt; 0.01). Moreover, agriculture-derived NH4+ contributed more than 54% of the total NH4+-N deposition in the CP period, being positively related to NH3 volatilization from cropland soil (p &lt; 0.05). The N concentrations were higher in the outlet water of ditches and runoff in May than in other months due to fertilization and irrigation. Therefore, to reduce the agricultural N losses and improve lake water quality, it is important to both reduce agricultural NH4+-N deposition from NH3 volatilization and intercept water flow from the paddy fields into drainage ditches during the CP.

Wood-Ash Fertiliser and Distance from Drainage Ditch Affect the Succession and Biodiversity of Vascular Plant Species in Tree Plantings on Marginal Organic Soil

Cutaway peatland is a marginal land, which without further management is an unfavourable environment for plant growth due to low bearing capacity, high acidity and unbalanced nutrient composition of the soil. After wood-ash application, the soil becomes enriched with P and K, creating better conditions for tree growth. In addition to being economically viable, tree plantations ensure long-term carbon storage and promote habitat restoration. In a three-year term, we studied how distance from a drainage ditch and three different doses of wood-ash—5, 10, and 15 tons per hectare—affect the diversity of vascular plants in a tree plantation on a cutaway peatland. Plant species richness, vegetation cover and composition were positively affected by the distance from the drainage ditch and application with fertiliser, but in most cases, fertiliser dose had no significant effect. Both cover and species diversity were not affected by the planted tree species. In a tree plantation, herbaceous plants provide soil fertility by decay and recycling, and reduce mineral leaching in the long term. Since vascular plants play an important role in both the development of habitats and tree growth, it is important to know how multiple factors influence the development of vegetation in tree plantations.

Influence of multi-timescale precipitation indices on primary tea production in Baoshan, Yunnan, China

The regional economy in Yunnan, Southwest China, relies heavily on tea production. Both the quality and amount of tea production are sensitive to extreme climate events, but exactly how different timescale climate events influence tea production remains unknown. In this study, we explore the dynamic responses of tea production indices in Baoshan, Yunnan to 6 multi-timescale precipitation indices (MPIs) at lags of up to 20 years. The results are as follows: (1) Wet injury caused by precipitation during summer and autumn is a prominent threat to annual tea production in Baoshan, which leads to negative impacts on annual tea yield and raw tea price, with the impact on the latter mainly reflected in tea quality during the primary processing for black tea and green tea. (2) Annual tea yield and raw tea price are negatively correlated with CDD (consecutive dry days) and R20 (very heavy precipitation days) at lags greater than one year. (3) Spring tea yield and raw tea price are negatively correlated with spring precipitation, but positively correlated with days in the winter-spring dormancy period of tea plant (WSDP) and precipitation in WSDP; the positive correlation of days in WSDP is the most prominent with spring tea production of the 3 MPIs. (4) Unlike other famous tea areas, lower R20 frequency in Baoshan is not associated with high rates of soil erosion, but the lack of drainage ditches in the tea garden still means that continuous precipitation or heavy rainfall are a risk to Baoshan tea production. The insights provided by this study will help farmers and other decision-makers to understand the mechanism of MPIs’ influence on tea production, inform regional responses in tea plantation management to the observed different precipitation trends, and improve future management decisions under a changing climate.

Optimal Design of Central Drainage Ditch Buried Depth for Highway Tunnel in Seasonally Frozen Region

In seasonally frozen regions, the drainage ditch of highway tunnels is usually set below the maximum frost depth. Hence, the deeply buried drainage ditch is often used, which increases the cost, difficulty, and time of tunnel construction. And it affects the stability of the surrounding rock and the tunnel structure safety. To solve these difficulties, this study investigated the optimal design of buried depth of central drainage ditch by numerical simulation. Based on a tunnel in Northwest China, a transient heat transfer model, which involves heat conduction and phase transition, was established. Then, the influences of different water amounts and thermal insulation technologies on the minimum buried depth of central drainage ditch were investigated. The results indicate that the thermal insulation layer, regardless of whether it is an internal thermal insulation layer, external thermal insulation layer, or foam concrete backfilled in invert arch, can prevent the drainage ditch from freezing and increase its elevation. The findings of this study can be helpful in optimizing the buried depth, selecting reasonable thermal insulation technology for central drainage ditch in seasonally frozen regions.

Modelling the impact of the agricultural holdings and land-use structure on the quality of inland and coastal waters with an innovative and interdisciplinary toolkit

The changes taking place in the marine coastal zones are extremely important, as about 40% of the human population currently lives in the coastal areas (within 100 kilometres of the coastline) increasing anthropogenic pressure on the marine ecosystems. Agriculture is a significant source of nutrients to the marine environment that increase hypoxia, eutrophication and may pose a threat to the services provided by ecosystems. In particular, surface water and submarine groundwater discharge (SGD) are dominant pathways of nutrient loads. The main aim of this study is to present the capabilities and results of an innovative and complex toolkit that enables researchers to identify the sources of nutrient and pesticide pollution, calculate their flux via rivers and SGD, and directly assess the influence of pesticides and nutrient flux on the coastal ecosystem. We combined the in situ sampling of surface water, groundwater, soil, SGD, and seawater with a model study to create a set of tools for assessing the influence of agriculture on the marine environment. The maximum concentrations of nitrates and phosphates were measured in the drainage ditches and were equal to 15.5 mg N-NO3− L−1 and 7.7 mg P-PO43− L−1 respectively. The nutrients concentrations varied from 0.1 to 12.9 mg N-NO3− L−1 and from 0.0 to 0.5 mg P-PO43− L−1 in all freshwater samples. In contrast, the lowest concentrations were observed in seawater with maximum levels of 0.8 mg N-NO3− L−1 and 0.1 mg P-PO43− L−1 respectively. The collected data were used to establish an innovative and interdisciplinary online toolkit in which surface run-off was modelled with Soil and Water Assessment Tool (SWAT), groundwater flow with Modflow, and marine waters using the EcoPuckBay model. Additionally, the tool includes two interactive calculators for calculation of the nutrient balance and nitrogen leaching for single fields on farms.

Plant communities in drainage ditches – conditions, characteristics and environmental functions

Ditches and drainage canals are an important element in the post-bog meadows. Their basic function is to regulate air-water relations in ecosystems, mainly in agrocenoses. The environmental functions of ditches and canals consist of maintaining a large diversity of flora and fauna species due to high humidity of these ecosystems. The study of plant communities in the ditches in the post-bog meadows habitat of the Supraśl Dolna valley structure in 2010–2020 was carried out. There were 23–27 species of plants in the ditches. Species diversity did not change significantly during this period, while changes in individual species’ coverage and viability were found. The species were classified into two rush communities: reed rush ( Phragmitetum australis) and rush ( Phalaridetum arundinaceae). As a result of the lack of maintenance of the ditches, an invasive species of flapped barbed ( Echinocystis lobata) was found. The natural valorization carried out by the Oświt method showed that plant communities in the drainage ditches are in the lowest valorization classes.

Analysis of the operation of the railway track in conditions of low-draining mares and high-temperature permafrost (on the example of the area of the Bureysky reservoir bypass).

The subject of research is the earthwork of the railway track and artificial structures on hazy weak-draining areas in the areas of permafrost distribution on the bypass of the Bureyskaya HPP reservoir within the Verkhnebureinskaya depression. The purpose is to identify the conditions and causes of adverse processes and phenomena that have arisen during operation. The objectives of the research are to identify the main causes and conditions for the manifestation of unfavorable geocryological processes and phenomena – waterlogging, flooding, stagnation of water, degradation of permafrost, sediment of the roadbed. Design errors are analyzed and recommendations are given for the application of design solutions in accordance with the state and dynamics of geocryological conditions and the requirements of the current regulatory documents for the areas of distribution of low-level marys and high-temperature permafrost. For the first time, a comprehensive analysis of the conditions and causes causing adverse processes and phenomena was carried out for the described territory. Inefficient constructions and design solutions have been identified. Optimal design solutions and measures are recommended to ensure the stable and safe operation of transport facilities in the region in conditions of low-drainpipe and high-temperature permafrost. For the studied area, the characteristic features are the significant swampiness of the territory, and the wide distribution of low– and high-temperature permafrost soils of the merging type. There are cases of irrational and inefficient design. It is not uncommon to use unsuitable soils for filling the roadbed and its elements. Also, the excess of the volume of earthworks during construction. Under these conditions, it is recommended: When designing a railway track plan, trace the line through local elevated terrain areas, in order to ensure the necessary slope of the design profile of drainage ditches of at least 4 ppm. Drainage ditches along the path should be located at a distance that excludes the inflow of water into the base of the roadbed.

Characterisation of Macrophyte Eleocharis dulcis for potential selected bioproducts

Overpopulation of macrophytes in drainage ditches can lead to a problem in maintenance and reduce the efficiency of the system. Therefore, this study aims to evaluate the feasibility of Eleocharis dulcis (E. dulcis) for bioproduct potential by chemical composition analysis. E. dulcis samples were collected from Parit Raja drainage ditch and sent to Malaysian Agricultural Research and Development (MARDI) for fibre content (cellulose, hemicellulose and lignin) and heavy metals (Cu, Pb, Zn) concentration. From the result, the fibre content of E. dulcis show the potential for bioethanol with an average value of 37.62% cellulose, 21.31% hemicellulose and 12.25% lignin. Meanwhile, Cu, Pb and Zn concentrations were 2.78, 0.63 and 2423.51 mg/kg, respectively. These values were low compared to WHO/FAO (2007), EN 13432 and Malaysia Food Regulations 1985, except for Zn, which has a slightly higher value indicating that it is suitable to be used as a bio-based straw. In conclusion, E. dulcis had the potential as biomaterial straws and bioethanol based on the chemical compositions. Therefore, the productions are recommended for further analyses of the bioproduct performances.

Nitrate Removal and Woodchip Properties across a Paired Denitrifying Bioreactor Treating Centralized Agricultural Ditch Flows

Treatment of nitrate loads by denitrifying bioreactors in centralized drainage ditches that receive subsurface tile drainage may offer a more effective alternative to end-of-pipe bioreactors. A paired denitrifying bioreactor design, consisting of an in-ditch bioreactor (18.3 × 2.1 × 0.2 m) treating ditch base flow and a diversion bioreactor (4.6 × 9.1 × 0.9 m) designed to treat high-flow events, was designed and constructed in an agricultural watershed (3.2 km2 drainage area) in Illinois, USA. Flow and water chemistry were monitored for three years and the woodchip and bioreactor-associated soil were analyzed for denitrification potential and chemical properties after 25 months. The in-ditch bioreactor did not significantly reduce nitrate concentrations in the ditch, likely due to low hydraulic connectivity with stream water and sedimentation. The diversion bioreactor significantly reduced nitrate concentrations (58% average reduction) but treated only ~2% of annual ditch flow. Denitrification potential was significantly higher in the in-ditch bioreactor woodchips versus the diversion bioreactor after 25 months (2950 ± 580 vs. 620 ± 310 ng N g−1 dry media h−1). The passive flow design was simple to construct and did not restrict flow in the drainage ditch but resulted in low hydraulic exchange, limiting nitrate removal.