A new Farm Package (FMP) was developed for using the U.S. Geological Survey's groundwater modeling program, MODFLOW-2000 (MF2K), to estimate irrigation water allocations to irrigation settings. The FMP dynamically integrates irrigation water demand, surface-water & groundwater supply, and return flow from excess irrigation. Routed surface-water delivery is optional, and can be simulated by coupling FMP with the Streamflow Routing Package (SFR1). MF2K with FMP and SFR1 allows estimating the allocation of surface-water and groundwater to farms for the following applications: (1) historic and future simulations, (2) water rights issues and operational decisions, (3) non-drought and drought situations. Irrigation demand, supply, and return flow are partly subject to head-dependent sinks and sources such as transpiration uptake from groundwater (formulated by FMP) and leakage between the conveyance system and the aquifer (formulated by SFR1). A steady state transpiration uptake, varying with changing water level, is stepwise linearly approximated by FMP. This was validated by ensembles of variably saturated soil column models using HYDRUS2D for different soil types, values of potential transpiration, and root zone depths. A restriction of transpiration uptake is proportional to a reduction of the active root zone. It is approximated in FMP by an analytical solution, which determines inactive ranges of the root zone with pressure heads typical for conditions of anoxia or wilting. At steady state, the transpiration uptake equaled the flux across the water table (plus the irrigation flux, if applied). Therefore, changes in soil water storage are assumed negligible. Based on this assumption, the irrigation flux required is determined in FMP by subtracting transpiratory components from natural sources (groundwater, precipitation) from a maximum transpiration uptake. This transpiratory irrigation requirement is calculated for each finite difference cell, and increased sufficiently to compensate for evaporative losses and for inefficient use. Accumulating the resulting cell delivery requirement over all cells in a farm yields the total farm delivery requirement, which is to be satisfied with surface- or groundwater. Five economic and non-economic drought response policies can be applied, if the potential supply of surface- and groundwater is insufficient to meet the crop demand. The code was verified by a hypothetical example problem run in 55 scenarios (5 drought policy scenarios x 11 parameter-group scenarios). Among all sources and sinks in a cumulative volumetric budget, 'farm well discharge,' and particularly 'farm net recharge,' were most sensitive to changes in drought policies or changes of parameters.

Bibliography: leaves 208-221. / xi, 229 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Study initiated with the objective of using evolutionary techniques instead of the gradient-based methods to solve the optimisation problems embodied in both management and inverse models. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1998

FLUMP, a recently developed mixed explicit -implicit finite -element program, was calibrated against a data base obtained from a portion of the Tucson Basin aquifer, Arizona, and represents its first application to a real -world problem. Two previous models for the same region were constructed (an electric analog and a finite -difference model) in which calibration was based on prescribed flux boundary conditions along stream courses and mountain fronts. These fluxes are not directly measured and estimates are subject to large uncertainties. In contrast, boundary conditions used in the calibration of FLUMP were prescribed hydraulic heads obtained from direct measurement. At prescribed head boundaries FLUMP computed time - varying fluxes representing subsurface lateral flow and recharge along streams. FLUMP correctly calculated fluctuations in recharge along the Santa Cruz River due to fluctuations in storm runoff and sewage effluent release rates. FLUMP also provided valuable insight into distributions of recharge, discharge, and subsurface flow in the study area.Properties of FLUMP were compared with those of two other programs in current use: ISOQUAD, a finite -element program developed by Pinder and Frind (1972), and a finite- difference program developed by the U.S. Geological Survey (Trescott, et al., 1976). It appears that FLUMP can handle a larger class of problems than the other two programs, including those in which the boundary conditions and aquifer parameters vary arbitrarily with time and /or head. FLUMP also has the ability to solve explicitly when accuracy requires small time steps, the ability to solve explicitely in certain parts of the flow region while solving implicitly in other parts, flexibility in mesh design and numbering of nodes, computation of internal as well as external fluxes, and global as well as local mass balance checks at each time step.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 134-138. / by Peter Kitanidis. / M.S.

No description available.

Hillslope mechanisms and processes are a complex and dynamic set of interactions, but are nevertheless vital components of hydrology due to their critical interactions with surface and groundwater (Lorentz, 2001a). In order to observe and quantify these flow generating mechanisms, the Weatherley subcatchment was selected where the components of streamflow generation have been studied and can be quantified separately. Surface, shallow subsurface and the deeper groundwater interactions are particularly important when quantifying runoff generation from within hillslope, riparian and wetland zones as they are the dominant runoff generating zones within the Weatherley catchment. These components of flow are important to quantify for the further study of flow generation mechanisms, their dynamics and fluxes at the hillslope and small catchment scale, low flow contributions, climate change as well as the consequences of land use change (Lorentz, 2001b). Transfer functions were found to be the best adaptation of hydrograph separation for distributed hydrological modelling purposes when attempting to quantify the various streamflow hydrograph components. In this study, the runoff components were simulated along transects using the HYDRUS-2D model, where the simulated soil water dynamics are compared with the observed tensions and water contents at different depths within the soil profile in order to quantify the contributing hillslope fluxes to streamflow generation. The 2001 data set was used with the rainfall and potential evapotranspiration data being converted into rates according to the breakpoint rainfall data. The HYDRUS-2D modelling exercise is performed to calculate the variety of flux rates (timing and quantities) within the subcatchment, so that the overall stream hydrograph can be properly deduced when modelling this catchment with transfer functions in the future. An understanding of the driving forces as well as the behaviour of sources and flow paths was extracted from this thesis, along with gaining some knowledge about the mechanisms and behaviour of streamflow generating mechanisms at the hillslope and small catchment scale. Troch et al (2003) clearly encapsulates the essence of modern day catchment hydrology in stating that hillslope response to rainfall remains one of the most central problems of catchment hydrology in order to quantify catchment responses. The processes whereby rainfall becomes runoff continue to be difficult to quantify and conceptualise (Uhlenbrook et al., 2003) and this is because the characterisation of subsurface water flow components is one of the most complex and challenging tasks in the study of the hydrologic cycle (Achet et al., 2002). Since trying to understand the temporal and spatial variability of moisture content and the subsurface flow mechanisms is a complicated problem (Achet et al., 2002), an attempt is made in this thesis to gain insights into the temporal and spatial variability of soil tensions and soil moisture content at various depths on hillslope transects by combining modelling exercises with field observations. From this modelling, the hillslope water balance and contributing fluxes are derived in effort to augment, at a later stage, the hillslope response functions. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Several hydrological studies claim that available water resources in a catchment are affected by large scale afforestation, especially where the regional rainfall is considered marginal for the support of silviculture. Nevertheless, the mechanisms and magnitude of the perturbations to the receiving water resources due to afforestation are still not clearly understood. To improve this understanding an intensive hydrological experiment has been initiated in the small grassed Weatherly catchment of the Mondi, North East Cape Forests. Details of the soil water dynamics on the Molteno formations in the catchment have been be studied. This research presents a description and first results of the establishment of an experiment which comprises monitoring the water budget of the grassed catchment prior to the afforestation of the catchment to plantations of exotic trees. The studies currently include, monitoring the infiltration and redistribution of soil water on a hillslope as well as monitoring of interflow mechanisms and localised mechanisms of soil water accumulation influenced by the topography and geology of the catchment. In addition to the intensive soil water monitoring, specific experimentation has been conducted at various locations on the hillslope. These comprise macropore flow process studies and 2-dimensional tracer experiments. Details of these experiments as well as the automated soil water and groundwater monitoring instrumentation are presented. An intensive soil survey on a 30 m x 30 m grid as well as a comprehensive measurement strategy of soil physical and hydraulic properties are highlighted. A review of 2-dimensional numerical hillslope soil water process models is also presented. Results from this research show that on hillslopes underlain by Molteno sandstones localised perched water tables form. These water bodies, upon reaching a critical height above the bedrock cascade downslope as interflow recharging the water bodies downslope. The response to infiltration increases downslope and in the toe region interflow occurs readily in response to rainfall compared to the midslope where substantial rain needs to infiltrate. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.

South Africa, in common with all countries with arid or semi-arid climatic conditions, is facing the consequences of irrigation development without effective subsurface drainage. The quality of irrigation water is also decreasing and hence more water is required for leaching. This is resulting in low irrigation water productivity, as a consequence of shallow water tables, thus limiting crop growth. This study investigated the nature and causes of shallow water table problems in the sugarcane fields of Pongola, South Africa. The DRAINMOD model was also assessed for its reliability to be used as drainage design tool in the area. A water table map of a 32 ha sugarcane field was generated using groundwater table data monitored in 36 piezometers from September 2011 to February 2012. Nearly 12 % of the 32 ha sugarcane field was found to be affected by shallow water tables of less than the 1.0 m Design Water Table Depth (WTD). The inability of the adopted Drainage Design Criteria (DDC) to cope with drainage needs was found to be the cause of the poor drainage problem. On the other hand, analysis of WTDs in a field with a poorly-maintained subsurface drainage system confirmed that the drainage problem is exacerbated by poor drainage maintenance. It was recommended that the subsurface DDC in the area be revisited and that timely maintenance also be provided The DRAINMOD model was calibrated and verified using actual WTD and Drainage Discharge (DD) data. The model evaluation results revealed that the DRAINMOD model can reliably predict WTDs, with a Goodness of fit (R2), Mean Absolute Error (MAE) and Coefficient of Residual Mass (CRM) of 0.826, 5.341 cm and -0.015, respectively. Similarly, the model evaluation results in predicting DDs were also good, with R2, MAE and CRM of 0.801, 0.181 mm.day-1 and 0.0004, respectively. A further application of the validated model depicted that drain pipes installed at depths ranging from 1.4 m to 1.8 m and a spacing ranging from 55 to 70 m, with a design discharge of 2.5 to 4.2 mm.day-1, were adequate in ensuring safe WTDs between 1.0 and 1.5 m in clay-loam soil. On the other hand, drain depths ranging from 1.4 to 1.8 m and spacing between 25 and 40 m, were found to be appropriate in maintaining WTDs between 1.0 and 1.5 m in clay soil, with drainage design discharge ranging from 2.5 to 5.1 mm.day-1. These findings suggest that the current drain spacing needs to be reduced, in order to maintain the 1 m design water table depth. Finally, for the adoptability of the DRAINMOD model in the area, the Rosetta program, a component of the HYDRUS-2D, was tested for its reliability in estimating saturated hydraulic conductivities required by the DRAINMOD model. Results of the investigation revealed that the program can reliably be used to estimate saturated hydraulic conductivities from easily accessed soil data (% sand, silt, clay and soil bulk density), with R2, MAE and CRM of 0.95, 0.035 m.day-1 and -0.031, respectively. Nonetheless, calibration of the DRAINMOD model based on saturated hydraulic conductivity estimated by the Rosetta program was recommended. The findings of this research will form the basis for implementing an agricultural drainage policy that will ensure sustainable rain-fed and irrigation crop production systems in South Africa. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

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