Hydrologic models HELP model

Schroeder, P.R., Dozier, T.S., Zappi, P.A., McEnroe, B.M., Sjostrom J.W., and Peyton, R.L., The Hydrologic Evaluation of Landfill Performance (HELP) Model Engineering Documentation for Version 3, EPA/600/R-94/168b, U.S. Environmental Protection Agency, Cincinnati, OH, 1994. 

This approach has been used in the well-known model HELP (Hydrological Evaluation of Landfill Performance, Schroeder et al. 1994) and a number of complementary models (Nixon et al. 1997). These models mostly assume the landfilled material to be idealized layers with homogenous properties. One such model, HYDRUS, has been used to model flow through Landfill Lostorf, but it was found that it could not fully catch the dynamics of flow, particularly after rain events (Johnson et al. 2001). Water passes through the... 

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... 

HELP Hydrologic Evaluation Landfill Performance Model... 

A large number of tools for modelling impacts in rivers have been developed and calibrated however, most of them simulate physical-chemical mechanisms and do not help assess the new issues introduced by the WFD, as, for instance, the impact of changes in hydrological regime or morphology. 

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