OBJTOP: A new model to simulate hydrological processes.

摘要

A new hydrologic model (OBJTOP) with a graphical user interface (GUI) was created using Object-Oriented Design (OOD) methods and the Objected-Oriented Programming (OOP) language-C++. OBJTOP is based on Beven's TOPMODEL concepts, but has been designed to relax some of the assumptions in Beven's original model.; A new methodology is developed to describe natural processes using C++. “Inheritance” is used to study individual objects (or processes) at multiple levels, while “aggregation” is used to study the interactions of objects (or processes). OBJTOP presents a description of hydrologic processes in a direct, concise and natural manner, more than in hydrologic models implemented in procedural languages.; The following mechanisms are included in OBJTOP: (1) saturation excess or the mixture of infiltration/saturation excess overland flow, (2) exponential or power law decay of hydraulic conductivity with soil depth, (3) topographic index (TI) or soil topographic index (STI) weighting of runoff likelihood, and (4) simulations with or without channel routing. By incorporating the above mechanisms into one model package, OBJTOP provides sixteen schemes for hydrologic simulations that can be applied to different watershed conditions and soil types. Further, OBJTOP allows a watershed to be divided into multiple sub watersheds for simulation, each with its own set of data, parameters and simulation schemes. Hence, the integrated simulation mechanisms of OBJTOP provide the opportunity to model heterogeneous watersheds. A mechanism in OBJTOP was developed to simulate hydrological processes in a watershed with unsewered septic systems.; The GUI provides an efficient manner for data input, parameter modification, simulation scheme selection and model calibration. Various kinds of graphical outputs are available, such as precipitation—runoff (total, subsurface, surface) in any selected simulation time period, TI or STI spatial pattern, water table distribution, water table (average, or associated with a TI/STI value) time series, etc.; OBJTOP has been applied to TOPMODEL web page data—Slapton Wood (http://www.es.lancs.ac.uk/hfdg/topmodel.html) and two watersheds in the New York City Croton drinking water supply watershed, Ward Pound Ridge (a natural forest) and B28 (a high density, unsewered residential area). The Nash-Sutcliffe criteria for the above three simulations are 0.913, 0.917 and 0.808, separately.