Abstract
Quantitative hydrologic modeling dates back to the middle of the nineteenth century. In the intervening period up to the middle of the 1960s, mathematical models were developed for individual hydrologic cycle components. These models were either empirical or were based mostly on systems theory or wave theory. However, in hydrologic practice in the real world, either empirical or systems-based models were predominantly employed and their employment continues in many parts of the world till today. With the advent of computer technology in the 1960s, the development of watershed models started with the Stanford Watershed Model published by Crawford and Linsley in 1966. In the subsequent two decades and a half, a large number of watershed models were developed by government agencies, universities, and private companies. If one were to count, the number of watershed models will easily approach 50 or perhaps even 100. The evolution of hydrologic models can be traced along four lines with overlapping chronology: (1) development of component models, (2) development of model science, (3) development owing to state and federal legislations, and (4) computer technology. With the expanding computing technology, emergence of information technology, introduction of new modeling tools, and development of space technology, watershed modeling entered into a new era. These days, watershed models are much more than typical hydrology models-they incorporate relevant aspects of allied sciences, such as hydrometeorology, climate science, geology, ecology, agriculture, sociology, risk analysis, and the like. This presentation will dwell upon three main theories-systems, wave, and entropy-which constitute the basis of most hydrologic component models. It then goes on to discussing watershed models which integrate these component models, modeling challenges, and future outlook.
Bio
Professor Vijay P. Singh is a Distinguished Professor, a Regents Professor, and the inaugural holder of the Caroline and William N. Lehrer Distinguished Chair in Water Engineering at Texas A&M University, USA. He received his B.Sc & Tech., M.S., Ph.D. and D.Sc. degrees, all in engineering. He is a registered professional engineer, a registered professional hydrologist, Board Certified Water Resources Engineer (ASCE-AAWRE), and an Honorary Diplomate of European Water Resources Association. He is a member of National Academy of Engineering (NAE), an Academician of Georgia Fazisi Academy, a member of European Academy of Sciences and Arts, and a fellow/member of 11 other international science/engineering academies. He is a Distinguished Member of ASCE, an Honorary Distinguished Member of IWRA, a Distinguished Fellow of AGGS, and an Honorary Member of AWRA, and a Fellow of AGU, EWRI, ASCE, IAH, ISAE, IWRS, and IASWC. He has published extensively in the areas of hydrology, irrigation engineering, hydraulics, groundwater, water quality, food-water-energy-environment nexus, water resources, entropy theory, copula theory, and climate change impacts.