Hydrologic models

The complexities of land surface response and runoff generation have also presented a major obstacle to global climate modelers. Hydrologic response is linked to several important climate feedbacks (see Section 6.4.2), so imtil the hydro-logic cycle, and in particular its land surface component, can be accurately represented, there is little hope for accurate assessments of global change. 

Tranter M, Sharp M, Lamb H, Brown G, Hubbard B, Willis I (2002) Geochemical weathering at the hed of Haut Glacier d Arolla, Switzerland - a new model. Hydrological Processes 16 959... 

Munoz-Carpena, R. (1993). Modeling hydrology and sediment transport in vegetative filter strips. Ph.D. Dissertation, North Carolina State University, Raleigh, NC, 242 pp. 

Cosby, B.J., Ferrier, R.C., Jenkins, A. and Wright, R.F. (2001) Modelling the effects of acid deposition Refinements, adjustments and inclusion of nitrogen dynamics in the MAGIC model. Hydrology Earth System Science, 5, 499-518. 

One of the first complete, continuous simulation models was the pesticide mnoff transport model (PRT) (56). Improvements in the PRT modelled to the hydrologic simulation program—FORTRAN model (57). A number of other models have been developed (58,59). These models represent a compromise between the avadable data and the abiHty to encompass a wide range in soils, climates, and pesticides. These models have had mixed success when extended beyond the data with which they were caHbrated. No model has yet been developed that can be proven to give accurate predictions of... 

INHECl is a front-end to the HEC-1 model developed by Hydrologic Engineering Center. 

Assists in modeling a watershed and creating the inputs to HEC-1 for hydrologic simulations. 

Bevin, K. J. and Kirkby, M. J. (1979). A physically based variable contributing area model of basin hydrology. Hydrolog. Sci. Bull. 23,419-437. 

Bonan, G. B. (1996a). A land surface model (LSM version 1.0) for ecological, hydrological, and atmospheric studies Technical description and user s guide, NCAR Tech. Note NCAR/TN-417+STR, Natl. Cent, for Atmos. Res., Boulder, CO. 

The existing tools to carry out an IWRM may include hydraulic and hydrological models, water quality models as well as knowledge bases containing the necessary knowledge for the optimal management of water resources. Besides, these tools... 

Any colony optimization (ACO) and swarm intelligence are forms of agent-based modeling inspired by colonies of social animals such as ants and bees [32]. ACO has become popular in engineering for optimal routing in water distribution systems [33, 34]. Particle swarm optimization has been successfully used to train ANNs, for instance, ANNs to predict river water levels [35], for parameter estimation, for example, in hydrology [36]. 

Newham LTH, Letcher RA, Jakeman AJ, Kobayashi T (2004) A framework for integrated hydrologic, sediment and nutrient export modelling for catchment-scale management. Environ Modell Softw 19(11) 1029-1038... 

Numerical models are used to predict the performance and assist in the design of final cover systems. The availability of models used to conduct water balance analyses of ET cover systems is currently limited, and the results can be inconsistent. For example, models such as Hydrologic Evaluation of Landfill Performance (HELP) and Unsaturated Soil Water and Heat Flow (UNSAT-H) do not address all of the factors related to ET cover system performance. These models, for instance, do not consider percolation through preferential pathways may underestimate or overestimate percolation and have different levels of detail regarding weather, soil, and vegetation. In addition, HELP does not account for physical processes, such as matric potential, that generally govern unsaturated flow in ET covers.39 42 47... 

The ET cover cannot be tested at every landfill site so it is necessary to extrapolate the results from sites of known performance to specific landfill sites. The factors that affect the hydrologic design of ET covers encompass several scientific disciplines and there are numerous interactions between factors. As a consequence, a comprehensive computer model is needed to evaluate the ET cover for a site.48 The model should effectively incorporate soil, plant, and climate variables, and include their interactions and the resultant effect on hydrology and water balance. An important function of the model is to simulate the variability of performance in response to climate variability and to evaluate cover response to extreme events. Because the expected life of the cover is decades, possibly centuries, the model should be capable of estimating long-term performance. In addition to a complete water balance, the model should be capable of estimating long-term plant biomass production, need for fertilizer, wind and water erosion, and possible loss of primary plant nutrients from the ecosystem. 

Surface runoff (Q) is the second-largest part of the hydrologic water balance for ET landfill covers at many sites in humid regions. Even at dry sites where surface runoff is small, errors in estimates of Q are important, and especially so if the model estimates significant Q on days with no runoff. Estimates of Q are therefore important to the design process at all sites. 

A better way to provide a safety factor is to utilize hydrologic factors that are known to affect soil-water use and storage. They may be used in combination with a model to evaluate options and... 

This section describes currently available models and presents important features of each that are pertinent to ET landfill cover design. These models have diverse origins however, each was intended for use in evaluating the hydrologic cycle and included features that are pertinent to landfill covers. The model developer and/or other reviewers have tested each of these models. The purpose of this evaluation is to determine the level of accuracy and usefulness of a model as it might be applied to ET landfill cover design and evaluation. 

Some models require calibration to optimize input parameters they are best used in a research setting where it is possible to make measurements with which to calibrate the model for a particular site. Appropriate measured hydrologic data are seldom available to calibrate a model for a particular landfill site. Therefore, engineering models used for ET cover design should not require calibration. 

Development of the Environmental Policy Integrated Climate (EPIC) model and its predecessor, the Erosion Productivity Impact Calculator, began in the early 1980s.69 70 The first version of EPIC was intended to evaluate the effects of wind and water erosion on plant growth and food production. More recent versions also evaluate factors important to other environmental issues. EPIC is a onedimensional model however, it can estimate lateral flow in soil layers at depth. All versions of EPIC estimate surface runoff, PET, AET, soil-water storage, and PRK below the root zone—these complete the hydrologic water balance for an ET landfill cover. 

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