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An understanding of the water balance of forest ecosystems is of benefit to foresters who manage second rotation stands. Maximizing the mean annual increment can be better realized if recognition is given to the importance of the water balance. One component of the water balance, root zone drainage, is not only important, but also difficult either to measure or calculate. In this study, root zone drainage during a two-week drying cycle was monitored by a method based on Darcy's Law. To implement the method, a tensiometer-pressure transducer system was developed which constantly monitored the soil water potential at five soil depths. The system was easily installed, required minimum maintenance and measured the potential of the soil water to within ± 1.8 cm. H₂O with a response time of less than five seconds. The cumulative root zone drainage for the two-week period was 11.72 mm. with an estimated maximum error of the daily drainage of ± 1.30 mm./day. Comparable root zone drainage derived from an independent but simultaneous evaluation by the water balance method was 9.33 mm. with an estimated maximum error of the daily drainage of ± 2.kl mm./day. Both positive and negative drainage to the root zone was observed. The negative drainage (water moving into the root zone) provides a supplementary supply of water to the root zone, thereby reducing the possibility of a soil water deficit occurring. / Forestry, Faculty of / Graduate

A study has been made to evaluate the effects of horizontal drain drainage on the water table drawdown in open pit slopes. Two major parameters of a horizontal drain drainage system, length and spacing, were studied. A two dimensional finite element computer model was constructed to simulate the water flow into drains in rock slopes. Water flow in the saturated zone was assumed. The computer model was tested by the field data obtained from the LORNEX Mine in British Columbia and the data taken from INTRODUCTION TO GROUNDWATER MODELING (Wang & Anderson, 1982). Satisfactory agreements were obtained. As the result of computer simulations, a series of graphs were plotted. These graphs show the relationship between hydraulic head distribution vs. drain spacing and length. They could be used in horizontal drain design as an aid to determine the spacing and length of a drain system. The computer simulations were also made to study the drainage characteristics of anisotropic rock slopes. The results indicated the influence of such rock conditions on the drainage effect. Another feature of mining slopes is that their height varies as the mining operation progresses. Therefore, the suitable vertical spacing between drain rows was investigated by computer simulation. A comparison of the drainage effects of different drain patterns, parallel drain and fanned drain layouts, was also made. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Subsurface drainage affects water table fluctuation patterns by removing the excess water from the soil. The annual average water table depths of the drained (A) and undrained (D) regimes are 0.83 and 0.48 m from the soil surface respectively. Subirrigation continuously provides water to the upper soil by capillary rise. The annual water table depths of the subirrigated regimes (B and C) are 0.61 and 0.70 m respectively. It is found that there is a significant curvilinear correlationship between the drainage flow rate and the water table height above the drain. Soil drainable porosity of different regimes was investigated by using the soil water balance approach. The average drainable porosity of regimes A and B are 6.0% and 4.9% from water table rise, and 5.9% and 4.5% from water table drawdown , respectively. Subirrigation adversely affects the soil drainable porosity. Soil drainable porosity is often considered as a constant. However, the results of this study indicate that it varies with the water table height above the drain. In the case of water table drawdown, this dependence can be successfully expressed by a negative exponential equation. In the case of water table rise, the correlation is not as significant, but there is still a trend that the drainable porosity decreases with the increase of the water table height above the drain. Evapotranspiration (ET) is often neglected in soil water balance models for the drain-able porosity determination. This may result in some errors. In this study, the potential ET rate was computed by the Penman and Hargreaves methods. These two methods give very similar ET values for the studied area. It is assumed that actual ET equals to the potential ET rate when the ground water table is close to the soil surface. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

This thesis is in four parts that report on the development of two procedures for the prediction of trafficability of tile-drained lowland soils in the Lower Fraser Valley of British Columbia. By these procedures one can predict trafficability either from soil water tension in the plough layer or from water table depth. A mathematical model developed in the Netherlands for the simulation of vertical non-steady flow of water in soils was tested by data collected in Spring from farmers' fields. The model predicted depth to the water table and, less accurately, tension in the top 15 cm in fields drained by tiles spaced at 30.5 m and 15.2 m. Cone penetration resistance (an index of soil strength) of soil in the field was found to be linearly dependent upon soil water tension between 0 and 100 - 175 cm of water. It was possible to predict the slope of this relationship for two mineral soils, but not for an organic soil. Trafficability tests with typical farm vehicles were carried out on one organic and two mineral soils at various degrees of wetness. Soil structure was significantly damaged after the first and third passes of the vehicles. The damage was greatest when the soil was near saturation. However, indices of structure could not be used per se as criteria for trafficable conditions. For each soil a relationship was established between soil strength and traction efficiency measured by wheelslip. A critical value of strength for trafficability was then obtained by using 20% wheelslip as a limiting value for traction efficiency. Reference to known strength-tension curves yielded critical tensions for trafficability. Soil strength was linearly dependent upon water table depth in Spring when evapotranspiration was small and when water table depth was less than 80 cm. Critical water table depths for trafficability inferred from this relationship were 53, 45, and 60 cm for Lumbum muck, Hallart silty clay loam (grassland), and Hallart silty clay loam (cultivated land), respectively. The effect of tile spacing on trafficability in Spring was assessed over a 2-year period. Evidence to support increased benefits due to the closer spacing was inconclusive in both soil types. When compared to undrained land the larger spacing of 30.5 m resulted in a significant increase in the number of trafficable days. Tile drainage was twice as important for the attainment of trafficable conditions in the muck as in the mineral soils. Two procedures for predicting trafficability of tile-drained farmland were described. Predictions by these procedures for two tile spacings in both soil types in Spring 1977 were within 3 days of one another and compared extremely well with dates on which measured water table depth and tension were considered adequate for trafficability. / Land and Food Systems, Faculty of / Graduate

Pore network models have served as a predictive tool for soil and rock properties with a broad range of applications, particularly in oil recovery, geothermal energy from underground reservoirs, and pollutant transport in soils and aquifers [39]. They rely on the representation of the void space within porous materials as a network of interconnected pores with idealised geometries. Typically, a two-phase flow simulation of a drainage (or imbibition) process is employed, and by averaging the physical properties at the pore scale, macroscopic parameters such as capillary pressure and relative permeability can be estimated. One of the most demanding tasks in these models is to include the possibility of fluids to remain trapped inside the pore space. In this work I proposed a trapping rule which uses the information of neighboring pores instead of a search algorithm. This approximation reduces the simulation time significantly and does not perturb the accuracy of results. Additionally, I included spatial correlation to generate the pore sizes using a matrix decomposition method. Results show higher relative permeabilities and smaller values for irreducible saturation, which emphasizes the effects of ignoring the intrinsic correlation seen in pore sizes from actual porous media. Finally, I implemented the algorithm from Raoof et al. (2010) [38] to generate the topology of a Fontainebleau sandstone by solving an optimization problem using the steepest descent algorithm with a stochastic approximation for the gradient. A drainage simulation is performed on this representative network and relative permeability is compared with published results. The limitations of this algorithm are discussed and other methods are suggested to create a more faithful representation of the pore space.

When a liquid drains through a hole in a container, a vortex may form between the surface and the drainage hole. An interesting phenomenon occurs in the presence of two drainage holes. Only one vortex forms, while the other hole will mostly drain as sink flow. In addition, the vortex can switch between one hole and the other with regular periodicity. The primary goal of this study is to measure this periodicity under varying conditions (height of water in the container, diameter of the drainage holes, and distance between drainage holes). Additionally, a study concerning the volume flow rates of vortical vs. sink flow out of the drainage holes was conducted. In the case of two drainage holes, when the height of the water was decreased in the container, the diameter of drainage holes decreased, or the distance between drainage holes was increased, the switching period was shown to decrease. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

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