Drainage Ditches Research Articles

Glyphosate-remediation potential of selected plant species in artificial wetlands

Glyphosate is a systemic herbicide with an important environmental impact due to its adverse effect on non-target organisms. Its removal can be accomplished by wild (native) plants which, together with their associated microbiota, have acquired tolerance against glyphosate or are able to degrade it. Little is known, however, about these plants' potential for glyphosate remediation and the role that plant-microbe interactions play in this process. The objective of the present study was to evaluate plant species from locations with a history of glyphosate exposure – drainage ditches of banana plantations (Musa sp.), or riparian areas - to determine which, in combination with their microbiota, promote the removal of glyphosate. Five plant species were selected to evaluate their response to inundated growing conditions and exposure to 20 mg glyphosate acid equivalent/L for 47 days. Parameters affecting plant growth and glyphosate removal were recorded. Rhizosphere bacterial strains were identified and their tolerance to different glyphosate concentrations determined. Also, the activity of 19 rhizospheric enzymes associated with the phosphorus, carbon and nitrogen cycles were analyzed. Glyphosate-treated Panicum maximum exhibited the highest removal efficiency (87%), followed by Typha domingensis and Heliconia latispatha. All plants were associated with glyphosate-tolerant bacteria, and in the cases of Xanthosoma sagittifolium and Fimbristylis dichotoma, strains were recovered that even succeeded in growing in a medium containing 40 g glyphosate ae/L. Processes involved in carbon, nitrogen and phosphorus metabolism in the rhizosphere were affected by glyphosate exposure, and the importance of plant-microbe-substrate interactions in the elimination of glyphosate was evinced. Although all plants contributed to the removal of glyphosate, their use in phytoremediation projects will depend on the location and nature of the environmental problem to be resolved.

Влияние уклона территории и систем дренажа на величину пожарного риска при перевозке горючих жидкостей автомобильным транспортом

В работе осуществлена оценка величины потенциального риска при перевозке пожароопасных грузов автомобильным транспортом с учетом возможного стекания горючей жидкости по уклонам. Проведено сравнение величины пожарного риска для случаев открытых и закрытых дренажных канав. It is not possible to calculate the fire risk that takes into account slopes on roads within the existing methodology for determining the calculated fire risk values at production facilities. The article suggests the elaboration of methodology considering the above-mentioned factors. The paper provides comparative assessment of the fire risk when transporting gasoline by automobile tanks with a capacity of 28 m, both considering one of the factors (road slope, the presence of drainage ditches) and without it. It is shown that these factors can have a significant impact on the fire risk value for objects near which there is an accident with a fire of vehicles with significant amount of flammable liquid. The potential risk increases approaching the lowest point of the road section. At the same time, depending on the total length of the section with a slope, this value may be an order higher than the fire risk in the areas located above. Technical measures such as drainage ditches can significantly affect the fire risk value. When open drainage ditches are installed, the risk of fire escalation increases when the burning liquid flows down. When installing closed drainage ditches, the risk of escalation due to the spread of fire is minimized and is possible mainly in the locations of drainage ditch hatches. At the same time, such technical solution increases the potential risk in the area of liquid discharge to the terrain.

Controlled Irrigation and Drainage Reduce Rainfall Runoff and Nitrogen Loss in Paddy Fields.

In southern China, the growing period of rice is synchronized with the rainy period, and the loss of nutrients (such as nitrogen) due to unreasonable irrigation and drainage, along with rainfall and runoff, has become the main source of agricultural nonpoint source pollution. The laws of runoff and nitrogen loss in paddy fields under different irrigation and drainage modes are not clear. In this study, field experiments were adopted to observe the runoff and nitrogen loss under typical rainfall and throughout the whole growth period. The results showed that, compared with the traditional irrigation and drainage mode, the controlled irrigation and drainage mode reduced the drainage of two typical rainfall processes by 47.5% and 31.3% and the peak drainage by 38.9% and 14.4%. Compared with those under the traditional irrigation and drainage mode, the average concentrations of total nitrogen, nitrate nitrogen, and ammonium nitrogen under the controlled irrigation and drainage mode were reduced by 22.2%, 22.7%, and 27.8%, respectively, during the whole rainfall process on July 21 and were decreased by 27.1%, 11.4%, and 25.6%, respectively, on August 25. In irrigated rice areas, under the controlled irrigation and drainage mode, drainage was reduced after two intercepts through paddy fields and drainage ditches. The nitrogen concentration in the drainage ditch decreased due to the increase in retention time and the effect of the ditch and field wetland. Compared with the traditional irrigation and drainage mode, the total nitrogen, nitrate nitrogen, and ammonium nitrogen loads of the controlled irrigation and drainage mode were reduced by 69.8%, 65.3%, and 69.7%, respectively.

Drainage ditches enhance forest succession in a raised bog but do not affect the spatial pattern of tree encroachment.

The study was conducted in the raised bog Kusowo (Baltic region, West Pomerania, Poland). Along a transect line crossing two open mires affected by forest succession we analysed tree age distribution. One of those mires had been drained in the past years and still retained some open ditches, while the other one was located far from the ditches. Every 10 meters along the transect line one tree was drilled at the root collar in order to determine its age. We also conducted phytosociological analyses and short-term water level measurements in the sample plots. We expected faster tree encroachment in the undisturbed part of the open mire. The results showed, that there were no significant differences in water table level and in soil moisture indicator values between the formerly drained and undisturbed open mire. There were also no statistically significant differences in tree encroachment between the disturbed and undisturbed mires. Location and the age distribution of the trees suggest that changes in the tree growth conditions cannot be directly explained by the general decreasing of water level in the bog, although periods following drainage works were associated with more numerous establishment of young trees, in the drained part of the bog as well as in the part not directly affected by drainage ditches.

Chlorpyrifos and Dimethoate in Water and Sediments of Agricultural Drainage Ditches in Northern Sinaloa, Mexico.

In northern Sinaloa state, Mexico, little is known on organophosphate pesticide transport and fate in agricultural drainage systems. Spatial and temporal variation of chlorpyrifos and dimethoate was assessed in two agricultural drainage ditches (Buenaventura and Burrión) and risk for aquatic life was estimated. Analysis was made by high performance liquid chromatography and risk estimates were determined following international reference frameworks. In water, the highest chlorpyrifos concentration in the Buenaventura ditch was 5.49µgL-1, and 3.43µg L-1 in the Burrión ditch. Dimethoate was quantified only once in both ditches (0.44µgL-1 and 0.49µgL-1). In sediment, chlorpyrifos was quantified only in the Burrión ditch (242µgkg-1). Chlorpyrifos concentrations surpassed water and sediment quality criteria, representing a hazard for environmental and human health, as both ditches discharge into the Gulf of California and are used for capture of commercial species such as the grey mullet (Mugil cephalus) and cauque prawn (Macrobrachium americanum).

Global importance of methane emissions from drainage ditches and canals

Globally, there are millions of kilometres of drainage ditches which have the potential to emit the powerful greenhouse gas methane (CH4), but these emissions are not reported in budgets of inland waters or drained lands. Here, we synthesise data to show that ditches spanning a global latitudinal gradient and across different land uses emit large quantities of CH4 to the atmosphere. Area-specific emissions are comparable to those from lakes, streams, reservoirs, and wetlands. While it is generally assumed that drainage negates terrestrial CH4 emissions, we find that CH4 emissions from ditches can, on average, offset ∼10% of this reduction. Using global areas of drained land we show that ditches contribute 3.5 Tg CH4 yr−1 (0.6–10.5 Tg CH4 yr−1); equivalent to 0.2%–3% of global anthropogenic CH4 emissions. A positive relationship between CH4 emissions and temperature was found, and emissions were highest from eutrophic ditches. We advocate the inclusion of ditch emissions in national GHG inventories, as neglecting them can lead to incorrect conclusions concerning the impact of drainage-based land management on CH4 budgets.

Abundance and Distribution of Malaria Vectors in Various Aquatic Habitats and Land Use Types in Kakamega County, Highlands of Western Kenya.

Management of malaria transmission relies heavily on vector control. Implementation and sustenance of effective control measures require regular monitoring of malaria vector occurrences, species abundance and distribution. The study assessed mosquito larval species composition, distribution and productivity in Kakamega County, western Kenya. A cross-sectional survey of Anopheline larvae was conducted in various aquatic habitats and land use types in Kakamega County, highlands of western Kenya between the month of March and June 2019. One thousand, five hundred and seventy six aquatic habitats were sampled in various land use types. The mean densities of An. gambiae s.l (46.2), An. funestus (5.3), An. coustani (1.7), An. implexus (0.13) and An. squamosus (2.0) were observed in fish ponds, burrow pits, drainage ditches, and tire tracks, respectively. High mean densities of An. gambiae s.l was reported in farmland (20.4) while high mean abundance of An. funestus s.l (8.2) and An. coustani s.l (4.0) were observed in artificial forests. The study revealed that the productivity of anopheles larvae varied across various habitat types and land use types. Therefore, treatment of potential breeding sites should be considered as an additional strategy for malaria vector control in Kakamega County, western Kenya.

Design and methodology for technological calculations of cable-winch traction plow ditchers

A current problem of drainage reclamation is the construction of a network of drainage canals or ditches. Existing technologies of an open drainage network ensure the use of single-bucket or rotary excavators, and with a ditch depth of up to 1 m it is required to use plow-type ditchers with two or three thrust tractors of T-170B type. It is possible to implement the required pulling forces for the operation of plow canal diggers using cable-winch draught. At the same time, a tractor with a winch-anchor passes, unwinding a tracking cable, along the route of the future channel, anchors and pulls the plow canal digger with the traction of the winch. On soils with a low bearing capacity, this principle of operation allows ensuring high flotation and efficiency factor, to realize the traction forces required for constructing a canal up to 1.7 m deep in one pass. Hereof it follows that the determination of the optimal design parameters of the units for forest reclamation work, as well as their mode work is relevant.

Weights of evidence modeling for landslide susceptibility mapping of Kabi-Gebro locality, Gundomeskel area, Central Ethiopia

Kabi-Gebro locality of Gundomeskel area is located within the Abay Basin at Dera District of North Shewa Zone in the Central highland of Ethiopia and it is about 320Km from Addis Ababa. This is characterized by undulating topography, intense rainfall, active erosion and highly cultivated area. Geologically, it comprises weathered sedimentary and volcanic rocks. Active landslides damaged the gravel road, houses and agricultural land. The main objective of this research is to prepare the landslide susceptibility map using GIS-based Weights of Evidence model. Based on detailed field assessment and Google Earth image interpretation, 514 landslides were identified and classified randomly into training landslides (80%) and validation landslides (20%). The most common types of landslides in the study area include earth slide (rotational and translational slide), debris slide, debris flow, rock fall, topple, rock slide, creep and complex. Nine landslide causative factors such as lithology, slope, aspect, curvature, land use/land cover, distance to stream, distance to lineament, distance to spring and rainfall were used to prepare a landslide susceptibility map of the study area by adding the weights of contrast values of these causative factors using a rater calculator of the spatial analyst tool in ArcGIS. The final landslide susceptibility map was reclassified as very low, low, moderate, high and very high susceptibility classes. This susceptibility map was validated using landslide density index and area under the curve (AUC). The result from this model validation showed a success rate and a validation rate accuracy of 82.4% and 83.4% respectively. Finally, implementing afforestation strategies on bare land, constructing surface drainage channels & ditches, providing engineering reinforcements such as gabion walls, retaining walls, anchors and bolts whenever necessary and prohibiting hazardous zones can be recommended in order to lessen the impact of landslides in this area.

The Larval Density of Mosquitos (Diptera: Culicidae) in Jiaxiang County, Shandong Province, China: Influence of Bacterial Diversity, Richness, and Physicochemical Factors

As Jiaxiang County of Shandong province is an area with complex mosquito vector composition, it is necessary to investigate the relationship between bacterial diversity, physicochemical factors, and larval density. Therefore, the physicochemical properties of 46 breeding sites for six kinds of habitat types (small puddles, small water containers, paddy fields, large water containers, irrigation channels, and drainage ditches) were investigated by a multiparameter analyzer; the water’s bacterial diversity was analyzed by the 16S rRNA full-length sequencing method. Spearman correlation and multiple linear regression were used to analyze the correlation between larval density and variables. The variables analyzed were dissolved oxygen, pH, hardness, turbidity, conductivity, temperature, ammonia nitrogen, water depth, and distance from the nearest house. One-Way ANOVA was used to understand whether there are differences in bacterial diversity in different habitats. Pearson linear correlation model was used to analyze the effects of bacterial diversity and richness on mosquito densities in breeding sites. A total of 3291 larvae were captured, and a total of 6 species of 4 genera were identified. The identified species were Culex pipiens pallens, Aedes albopictus, Anopheles sinensis, Culex tritaeniorhynchus, Culex bitaeniorhynchus, and Mansonia uniformis. The density and species can be jointly affected by physicochemical properties and bacterial diversity, especially Shannon index and distance from the nearest house. In general, the physicochemical parameters and bacterial diversity of different habitats were significantly different. Even for the same habitat type, the physicochemical parameters varied greatly due to different environments.

A Review of On-farm Roadway Runoff Characterisation and Potential Management Options for Ireland

Runoff from farm roadways within farm boundaries are acknowledged as a year-round source of pollutants discharging to surface water, particularly during the main grazing season (Feb-Nov) when their usage is high. These losses are considered to be a significant catchment scale pressure and have led to recent legislation in Ireland to prohibit direct runoff from farm roadways to waters with similar guidance in the UK and New Zealand. However, roadway runoff (RR) remains an undocumented and understudied part of the transfer continuum where knowledge gaps remain in relation to its quantity and composition and in relation to the impacts of RR management options on adjacent surface waters. Indeed some information on mitigation measure design and efficacy is only available from non-agriculture land uses e.g. forestry and needs to be presented in a farm specific context. The present review brings together knowledge on RR in terms of content on- or off-roadway management options and proposes alternative mitigation measures that may require pilot scale testing. Studies show that RR contains a mix of legacy (surface materials) and incidental (fresh urine and faeces) constituents such as phosphorus (P), Escherichia coli (E. Coli) and sediment which become temporarily mobilised during rainfall events. Once mobilised, the roadway network can quickly transport pollutants providing connectivity between farmyards, hard standings, underpasses where attached to a watercourse, fields and even public roadways to watercourses. Its contents are not dissimilar to dilute slurry or dairy soiled water with loads being highest where animals congregate (within 100 m of the farmyard or where roadway configuration or quality impedes stock movement along the network). On-roadway management options include regularly spaced diversion structures that divert runoff for passive treatment in a field or drainage ditch or the application of chemical amendments to roadway surfaces. Off-roadway options can include natural or enhanced features, which attenuate flow leading to settlement of suspended sediment and in some cases treatment of a percentage of the load before delivery to a watercourse. It should be noted that the options presented in this review need to be retrofitted to site specific conditions. Therefore, a number of factors, including their effectiveness, cost and management needs on a particular farm, as well as local regulation requirements will need to be considered prior to implementation. Therefore, only the measures that divert RR away from waters are applicable to Ireland. Future research should develop and validate a farm roadway risk assessment tool to identify vulnerable roadway sections that need management and/or re-design, and identify means of incorporating RR into catchment scale risk assessment models. In addition, design of on- and off-RR management options should consider the wide variations in farm configuration and management with regard to size, topography, soil type/drainage class, enterprise, intensity, scale, stage of development and the potential impacts of climate change.

Research on waterproofing and drainage optimization scheme for karst tunnel lining in water-rich areas

In the presence of heavy rainfall on the earth’s surface, a series of water-induced problems often appear in karst tunnels, such as lining cracks and invert uplift. An effective method of alleviating these problems is the adjustment of the tunnel drainage scheme. In this study, three waterproofing and drainage optimization schemes were studied using numerical simulation and model tests. Numerical results show that, when the conventional waterproofing and drainage scheme is adopted in water-rich karst tunnels, the water pressure at the tunnel invert cannot be effectively reduced by the drainage system. When the water head height of the tunnel crown is 50 m and the distance between circumferential drainage blind pipes is reduced from 5 to 2 m, the rate of water pressure reduction at the invert from 21 to 27%. When a longitudinal drainage blind pipe is added at the bottom of the invert, the rate of reduction is increased to 84%; however, it is increased to 96% when the central drainage ditch is set at the bottom of the invert. Therefore, placing the central drainage ditch at the bottom of the invert has the most significant effect on reducing the water pressure. Model test results indicate that when the water head height of the tunnel crown is 12 m, the reduction rates of water pressure at the invert corresponding to the placement of a central drainage ditch at the bottom of the invert are 66%. The model test results were found to be consistent with numerical results.

NOVEL INTRODUCTION FOR THE INVASIVE RED-RIM MELANIA MELANOIDES TUBERCULATA (MÜLLER) IN SOUTHEASTERN TEXAS

Specimens of the invasive red-rim melania snail, Melanoides tuberculata, were observed in concrete drainage ditches throughout Jefferson County, Texas, from May 2018 to September 2019. The species appears to be well established in this artificial habitat, with a population disjunct from other established areas in central Texas and southeastern Louisiana. This occurrence in Jefferson County is likely the result of an aquarium release event independent of other release events for this species and subsequently spread by tropical storm activity.

Feasibility of improving nitrogen removal by integrating the rice straw and zeolite with drainage ditches for farmland runoff control

Natural zeolite and rice straw have been widely used for removing nitrogen (N) from wastewater due to their different N removal mechanisms. In this study, the N removal performances of three substrate systems composed of zeolite (Z), rice straw (R) and their combination (ZR) were assessed for decontaminating farmland runoff characterized by high loads of ammonium - N or nitrate - N besides of a low carbon content. The N-cycling functional genes were also investigated. The results showed that ZR achieved significantly higher ammonium (48.9%–77.7%) and TN (39.7%–65.9%) removal rates than Z and R ( P < 0.05). ZR also exhibited the highest removal rates of nitrate (67.6%–82.7%) and TN (45.5%–62.1%) in nitrate wastewater treatment. The abundances of 16S rRNA and denitrifying genes (including nirK , nirS , narG and napA ) were significantly enhanced in ZR, which partly explained the higher N removal in the ZR than in the Z and R systems. These findings suggest that it is feasible to combine rice straw with zeolite as a substrate of drainage ditches for considerable N removal enhancement in the control of agricultural runoff. • ZR showed the highest nitrogen (N) removal rate when both NH 4 + -N and NO 3 − -N wastewaters were treated. • TN and NO 3 − -N removal in Z was limited by insufficient denitrification due to low organic carbon source. • The combination of zeolite and rice straw significantly increased the abundances of 16S rRNA and denitrifying genes.

Mapping Subsurface Seepage Flow Patterns in Proximity to a Coal Combustion Residual Landfill Using Electrical Resistivity Tomography

Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.

Wild Paradise: Hope in the Great Dismal Swamp

Wild Paradise: Hope in the Great Dismal Swamp Ridwaana Allen Although the Great Dismal Swamp is as formidable as it sounds, there is so much more to its story. A forested peatland straddling the North Carolina/Virginia border, this mixture of forests and marshes is home to 119 varieties of wildflowers, 54 tree species, 41 kinds of shrubs, 35 aquatic plant species, 29 ferns and vines, along with 81 grasses, sedges, and rushes (Mohlenbrock 2012). Over 200 species of birds have been identified at the swamp, with 93 reported to nest there. Other inhabitants include various reptiles and amphibians, otters, bats, raccoons, minks, foxes, gray squirrels, white-tailed deer, and less commonly, black bears and bobcats (Wilson 2001). The Great Dismal Swamp’s past is as rich as its biodiversity. The swamp is full of narratives, some conflicting. To early settlers, it was a wilderness to be tamed. To poets and writers, it was inspiration. To Native Americans, Africans, and African Americans, it was a refuge – an alternative to colonialism and slavery. When the English first began exploring the Virginia lowlands in the 1600s, “dismal” meant “swamp” in that region, and the terms were used interchangeably (Tidwell 2002). In 1728, William Byrd II, a colonel in the British army and wealthy plantation owner, led a group of surveyors into the swamp to help demarcate the border between Virginia and North Carolina (Hansen 2010). Colonel Byrd – who believed that the Great Dismal Swamp and its air were so foul, no living thing could survive there, and birds would not fly over it – is credited with naming it (ibid.). After his visit, Colonel Byrd wanted to drain the swamp and turn it into an extensive hemp farm. He also wanted to use canals to connect the swamp to the Pasquotank River in North Carolina to the Elizabeth River in Virginia (Tidwell 2002). After traveling the swamp on horseback, George Washington described it as a “glorious paradise.” He wanted to build a north-south canal to connect Chesapeake Bay and the Albemarle Sound (Pettie 1976). In 1763, Washington’s Great Dismal Land Company started clearing the swamp for rice farming (Belcastro 1998). When that venture failed, they turned to logging, which was much more profitable. Drainage ditches and roads were built to facilitate the logging (Belcastro 1998). Later in the 1760s, a canal known as “Washington’s Ditch” was dug between Lake Drummond and the Nansemond River (Pettie 1976). In the 1790s, the Dismal Swamp Canal was dug (Mohlenbrock 2012). Both remain to this day. Worth mentioning is that most excavation, production, and transport was accomplished using Black slave labor (Sayers et al. 2007). [End Page 1] Arguably, the Great Dismal Swamp exists as much in the physical as in the imagination. It served as literary inspiration for Robert Frost, and as the backdrop for other writers including Thomas Moore’s “The Lake of the Dismal Swamp,” Harriet Beecher Stowe’s novel, Dred, and Henry Wadsworth Longfellow’s “The Slave in the Dismal Swamp” (Pettie 1976). While the Great Dismal Swamp may have inspired capitalistic resource exploitation, poetry, and prose, others had different motivations. Between circa 1630 and 1860, Native Americans and thousands of African Americans occupied the swamp (Sayers 2006). While it remains unknown how many Native Americans occupied the swamp, African Americans numbered in the thousands as maroons and enslaved laborers (ibid.). Three time periods appear to emerge, along with corresponding geographies. According to archaeological finds, disenfranchised Native Americans likely lived along the swamp edges to maintain selective access to the outside world between 1630 and 1710 (Sayers et al. 2007). One form of resistance to the cruelty and inhumanity of slavery was marronage, which is “the act of removing oneself from enslavement or running away” (Agorsah 1994). Between 1700 and 1865, maroons occupied swamp edges, small islands, and the interior (Sayers et al. 2007). Enslaved laborers occupied the swamp between 1765 and 1865 in canal-adjacent areas, and performed various tasks including canal excavation, barge pushing, and shingle making (ibid.). Hiding in plain sight, at least one maroon community worked among the enslaved individuals and free Black and White laborers for the construction of railroads (Maris-Wolf 2013). The groups...

ПРИНЯТИЕ РЕШЕНИЯ ПО ВЫБОРУ ТИПА УКРЕПЛЕНИЯ ВОДООТВОДНЫХ И НАГОРНЫХ КАНАВ НА ОСНОВЕ МЕТОДА ИДЕАЛЬНОЙ ТОЧКИ

Modern materials and technologies for strengthening drainage and upland ditches, their advantages and disadvantages are considered. When choosing the type of reinforcement, the railway design engineer must compare the options for the types of reinforcement of ditches in terms of various criteria: reducing labour and resource intensity, duration of construction work, increasing durability, improving environmental friendliness, the need for special equipment, and others. An ideal point method is proposed for solving a multicriteria deterministic problem of choosing the type of ditch reinforcement. A prototype program of the decision support system for choosing the type of reinforcement using the ideal point method has been developed. The program contains four areas: the source data area; the calculation area; the guide to the types of ditch reinforcement, which separately identifies innovative types of ditch reinforcement; the area of calculation results and recommendations. With the help of the program, the test problem of choosing the type of reinforcement is solved. Of the three alternatives, a concrete roadbed is recommended-an innovative strengthening of the ditch.

Processes controlling the flux of legacy phosphorus to surface waters at the farm scale

Phosphorus (P) leaching from agriculture is a major driver of water eutrophication in downstream rivers and lakes. In drained lowland areas with intensive agriculture, a reduction in the fertilizer applications may be insufficient to improve the water quality in the short term as the P accumulated in the soil during decades of high fertilization may continue leaching for many years. A complementary approach to reduce P exports from agriculture is to implement edge-of-field mitigation measures at the farm scale. The selection of effective measures requires a detailed insight into the chemical and hydrological transport mechanisms. Here, we determined the main P sources, processes, and transport routes at the farm scale to support the selection of appropriate mitigation measures. We quantified the legacy P, the different P pools stored in the upper soil, and related it to the yearly P export downstream. To do this, we combined high-resolution monitoring data from the soil, groundwater, surface water, and ditch sediments. The legacy P in the topsoil was high, about 2500 kg ha−1. The predominant subsurface flow and the subsoils’ P sorption capacity retained the P mobilized from the topsoil and explained the relative moderate flux of P to surface waters (0.04 kg ha−1 during the 2018–2019 drainage season). The dissolved P entering the drainage ditch via groundwater discharge was bound to iron-containing particles formed due to the oxidation of dissolved ferrous iron. Once leached from the soil to the drainage ditch, resuspension of P-rich sediment particles during flow peaks were the most important P transport mechanism (78%). Therefore, we expect that hydraulic constructions that reduce flow velocities and promote sedimentation of P-containing particles could reduce the export of P further downstream.

Seasonal and temporal factors leading to urea-nitrogen accumulation in surface waters of agricultural drainage ditches.

Urea-nitrogen (N) is commonly applied to crop fields, yet it is not routinely monitored despite its association with reduced water quality and its ability to increase toxicity of certain phytoplankton species. The purpose of this work was to characterize temporal fluctuations in urea-N concentrations and associated environmental conditions to infer sources of urea-N in agricultural drainage ditches. Physicochemical properties and N forms in ditch waters were measured weekly during the growing seasons of 2015-2018. Fertilizer application was only associated with spring peaks of urea-N concentrations in ditches next to cornfields, whereas summer peaks in ditches adjacent to corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields were not associated with fertilizer applications. Environmental conditions of warmer temperatures, lower dissolved oxygen concentrations, and lower redox potentials were correlated with higher urea-N concentrations. In 2018, peaks of urea-N and ammonium-N during the summer co-occurred with peaks of dissolved organic N and total dissolved N, suggesting they might be associated with the breakdown of organic matter and with the turnover of the organic N pool. Although the highest urea-N concentrations occurred when ditch surface waters were hydrologically disconnected from nearby streams, heavy rainfalls can potentially flush accumulated urea-N into coastal waters, where it may affect algal bloom toxicity. Therefore, implementation of available drainage ditch management practices is recommended, but these strategies need to be optimized for targeting periods with high rainfall that coincide with fertilizer additions as well as for periods with low rainfall that promote stagnant water conditions.

The impact of beaver dam removal on the chemical properties of water in drainage ditches in peatland forests

ABSTRACT Despite near-extinction in the nineteenth century, after efficient restoration measures the population of Eurasian beaver (Castor fiber L.) in Latvia currently is viable and growing. While the ecological effect of the species on water quality and biodiversity is generally positive, the high number of animals in production forests often creates challenges for management. Drainage ditches are among the most favoured habitats of beavers resulting in flooded stands, reduced tree growth and economical losses. The aim of the study was to evaluate the chemical properties of water in forest drainage ditches, affected by beaver activity, and their changes after the dam removal. Chemical composition of surface water in ditches was analysed in sampling points above dam, below dam and in the ditch itself after removal of the dam; results compared to pristine beaver site nearby on a small stream. Results did not show significant differences between concentrations above and below dams. After removal of the dams, significant increase in DOC, N-NO3 -, N-NH4 + and TSS concentrations and significant decrease in TP concentrations were observed in some of the sites. Observed concentrations of all measured parameters were significantly lower in pristine beaver site than in beaver sites on drainage ditches.