Search

Extensive use of drainage ditches in European boreal forests and in some parts of North America has resulted in a major change in wetland and soil hydrology and impacted the overall ecosystem functions of these regions. An increasing understanding of the environmental risks associated with forest ditches makes mapping these ditches a priority for sustainable forest and land use management. Here, we present the first rigorous deep learning–based methodology to map forest ditches at regional scale. A deep neural network was trained on airborne laser scanning data (ALS) and 1,607 km of manually digitized ditch channels from 10 regions spread across Sweden. The model correctly mapped 86% of all ditch channels in the test data, with a Matthews correlation coefficient of 0.78. Further, the model proved to be accurate when evaluated on ALS data from other heavily ditched countries in the Baltic Sea Region. This study leads the way in using deep learning and airborne laser scanning for mapping fine-resolution drainage ditches over large areas. This technique requires only one topographical index, which makes it possible to implement on national scales with limited computational resources. It thus provides a significant contribution to the assessment of regional hydrology and ecosystem dynamics in forested landscapes. [ABSTRACT FROM AUTHOR]

Surface water impoundment in an unlined triangular ditch during a single managed aquifer recharge (MAR) infiltration pulse lasts for time Te , after which all initially disposed water seeps into a homogenous isotropic coarse soil. In ditches with initial water W0 with depth H0 and length L , the dyad (W0,H0) vanishes at t→Te. The ditch slope that minimizes an objective function involving a linear combination of Te , W0 , and H0 with arbitrary cost coefficients was found. The analytical expression for Te as a function of the bank slope and the sand's porosity is for soils without capillarity and mild bank slopes. An isoperimetric constraint in optimization is the volume of the water pulse released into the ditch. A global unique minimum exists if the coefficients factoring W0 and H0 are not identically zero. A numerical solution to a two-dimensional infiltration problem was obtained using HYDRUS 2D/3D and its reservoir boundary condition option for arbitrary soils and bank slopes. Optimal slopes of triangular ditches were found for an initially dry loam. The analytical and numerical optimal shapes were not sensitive to mild variations of the ditch slope. [ABSTRACT FROM AUTHOR]

Spatiotemporal information on historical peatland drainage is needed to relate past land use to observed changes in catchment hydrology. Comprehensive knowledge of historical development of peatland management is largely unknown at the catchment scale. Aerial photos and light detection and ranging (LIDAR) data enlarge the possibilities for identifying past peatland drainage patterns. Here, our objectives are (1) to develop techniques for semiautomatically mapping the location of ditch networks in peat-dominated catchments using aerial photos and LIDAR data, and (2) to generate time series of drainage networks. Our approaches provide open-access techniques to systematically map ditches in peat-dominated catchments through time. We focused on the algorithm in such a way that we can identify the ditch networks from raw aerial images and LIDAR data based on the modification of multiple filters and number of threshold values. Such data are needed to relate spatiotemporal drainage patterns to observed changes in many northern rivers. We demonstrate our approach using data from the Simojoki River catchment (3,160 km²) in northern Finland. The catchment is dominated by forests and peatlands that were almost all drained after 1960. For two representative locations in cultivated peatland (downstream) and peatland forest (upstream) areas of the catchment; we found total ditch length density (km=km²), estimated from aerial images and LIDAR data based on our proposed algorithm, to have varied from 2% to 50% compared with the monitored ditch length available from the National Land survey of Finland (NLSF) in 2018. A different pattern of source variation in ditch network density was observed for whole-catchment estimates and for the available drainedpeatland database from Natural Resources Institute Finland (LUKE). Despite such differences, no significant differences were found using the nonparametric Mann-Whitney U test with a 0.05 significance level based on the samples of pixel-identified ditches between (1) aerial images and NLSF vector files and (2) LIDAR data and NLSF vector files. [ABSTRACT FROM AUTHOR]

A steady-state analytical solution is proposed for computing three-dimensional seepage into a partially penetrating ditch drainage system receiving water from an uneven ponding field of finite size. The draining soil is assumed to be saturated, homogeneous, and anisotropic, resting on an impervious stratum. The correctness of the proposed model was checked with the analytical and experimental results for a simplified case. A numerical comparison was also carried out between the proposed analytical model and the corresponding finite-difference model for a given flow condition. The study highlights the significance of drain width, penetration depth, ponding distribution, and anisotropic ratio on the discharge distribution from the side and bottom face of the drains. In ditches of shallow depth, a significant rise in the percentage of bottom flow was found in soil with a low anisotropic ratio. With the introduction of the uneven ponding field, considerable enhancement in the contribution of flow discharge from the bottom face of the drain was observed. Travel time and orientation of flow paths were found sensitive to the point of release at the soil surface. Moreover, partially penetrating ditches promote a highly curved flow path from the surface to the recipient drain which in turn increases the travel time of the water particle. [ABSTRACT FROM AUTHOR]

Drainage ditches are effective agricultural facilities because they can drain excess water from the field, and an eco-friendly drainage ditch can also eliminate agricultural nonpoint source pollution effectively. Field work has been conducted in four types of drainage ditches with different revetment techniques, i.e., a two-stage ditch with a woodpile bank, a single trapezoidal ditch with a geotextile bag, a hollow hexagonal brick, and a reinforced vegetative bank revetment. The corresponding retention capacity of phosphorus in these ditches has been investigated. Results show that two-stage ditches can retain dissolved phosphorus (DP) more effectively compared to the other three single trapezoidal drainage ditches, and the retention efficiency is as high as 60%. The concentration of total suspended sediment (TSS) is positively correlated with that of total phosphorus (TP), and the retention capacity of drainage ditches on phosphorus will decrease as discharge increases. Current work proves that a well-designed two-stage section ditch can effectively eliminate the nonpoint source pollution during practical agriculture drainage application. [ABSTRACT FROM AUTHOR]

The government has provided financial assistance on approximately 200 tailwater recovery systems in the state of Mississippi, and more in other states. The objective of this study was to quantify surface water capture and use within 31 tailwater recovery ditches (TWR) and on-farm storage reservoirs (OFS), so that conservation benefits could be evaluated. Water-level data were combined with system dimensions, rainfall data, and evaporation estimates to assess total gains and losses over the course of a year. Systems had a net positive balance of approximately 2,200,000 m³ (2,200 ML) of captured surface water. Losses from evaporation and infiltration were between 8.68 and 10.97 mm d-1 for TWR and 4.96 to 8.40 mm d-1 for OFS. The highest losses occurred in the fall for TWR due to the installation cycle, whereas they were highest in the summer for OFS, driven by evaporation. Producers irrigated with an average of 41,000 m³ (41 ML) (TWR) and 84,000 m³ (84 ML) (OFS) of surface water. Irrigation levels were generally below thresholds set by the government for sufficient use. [ABSTRACT FROM AUTHOR]

A methodology for optimal spacing in an array of ditches fully penetrating into homogeneous and isotropic porous medium of finite depth over an impervious layer is presented. The cost function includes the depth-dependent earthwork cost and the capitalized cost of pumping of drain discharge. Essentially, it is a problem of minimization of a nonlinear objective function of single variable. The input variables consist of rainfall intensity, hydraulic conductivity of the porous medium, width and depth of ditches, earthwork cost, cost of pumps and pumping energy cost, efficiency of pumping unit, and rate of interest. Using nonlinear data fitting method an explicit equation has been proposed for computing the optimal spacing between the ditches. [ABSTRACT FROM AUTHOR]

A comprehensive analytical solution for the quantity of seepage into an array of fully penetrating ditches from a ponded surface has been obtained using hodograph and Schwarz–Christoffel transformation. The solution includes equations for the quantity of seepage from the seepage face part as well as the water depth part of the ditch. The solution also comprises expressions for the velocity potential at the stagnation point and the variation in seepage velocity. The variation in seepage quantity is like the shape of a curved channel whose boundary maps along a circle onto the hodograph plane. This shape is average of a semiellipse and a parabola. The seepage contribution from the nonseepage face is maximum for half full condition and it is half of the total seepage in an empty ditch (full seepage face). Irrespective of the spacing between ditches the quantities of seepage from the seepage face part and the nonseepage part are equal for one third full ditch. The solution also deals with special cases like single ditch, unequal spacing between ditches, and unequal depth of water in adjacent ditches. The expressions the quantity of seepage have been simplified in explicit algebraic equations through minimization of errors. The simplified expressions, which are near exact, result in answers in single step computations. Also, an example and graphs have been included to demonstrate the sensitivity of the parameters. [ABSTRACT FROM AUTHOR]

This study presents both a numerical and an experimental solution to seepage from a rectangular ditch or elongated pond to a groundwater table of infinite horizontal extent. Because of the unknown location of the free surface, the flow domain is transformed into the complex potential plane using the inverse formulation method, where the free surface becomes a straight line. The method of finite differences was used to solve the boundary value problem. The problem was also investigated experimentally using a sand tank model. For comparison purposes, a one-dimensional analytical solution is also presented. The results were compared with each other and with those available in the literature obtained with other solution techniques. The parameters affecting the seepage rate were investigated and the resulting relationships are presented in dimensionless graphs. It is believed that these graphs may be of use in design problems. The conditions for which the simplified one-dimensional analytical solution agrees well with the results of the sophisticated two-dimensional numerical solution are identified. [ABSTRACT FROM AUTHOR]

Features a study which proposed a numerical solution of two dimensional free surface flow to the problem of ground-water flow to ditch drains in anisotropic soils. Methodology of the study; Results and discussion; Conclusion.

Describes solutions to the problem of seepage rainfall or irrigation recharge into homogeneous and anisotropic soil medium, drained by equally spaced ditch drains overlying a barrier. Geometry for steady drainage of an anisotropic soil by equally spaced ditch drains laid on an impermeable barrier; Steady-state theory for ditch drains dug down to an impervious barrier and gravel substratum.

The construction of a new barrage, the Gangjeong–Koryeong Barrage, in the Nakdong River and related sluice-gate operation has resulted in higher river-water and groundwater levels in the floodplain, which has caused the land to become swampy. The barrage construction caused changes in the groundwater flow direction and amounts of inflow and outflow between the river and surrounding area. The river has been the source of most of the groundwater in the riparian zone due to river leakage (from 96 to 1,975 m3/day) since being dammed. Two methods were proposed to lower the groundwater level in the swampy area: a drainage channel system and a pumping well system. Numerical simulations to assess the effectiveness of each method were performed, and the pumping well system was shown to be the more effective of the two. Following the construction of a drainage system consisting of eight pumping wells, the groundwater levels returned to predam levels. This study shows that the hydrological effects of high river-water levels in the riparian zone need to be examined thoroughly when a river barrage is designed and constructed. [ABSTRACT FROM AUTHOR]