Historical Development of Hydrology

Why did Chow call 1930-1950 as period of rationalization for hydrology?

Chow called the period from 1930-1950 as the Period of Rationalization because it produced a significant step forward for the field of hydrology, as government agencies began to develop their own programs of hydrologic research.

What were the important research outputs during this period?

Sherman’s unit hydrograph (1932), Horton’s infiltration theory (1933), Theis’s nonequilibrium equation (1935), and Gumbel’s extreme-value distributions for frequency analysis of hydrologic data (1958) are some of the important research outputs during the 1930s to 1950s. These outputs advanced the state of hydrology in very significant ways.

The unit hydrograph (originally named unit-graph) which was first proposed by Sherman (1932) is a simple linear model that can be used to derive the hydrograph resulting from any amount of excess rainfall.

The Horton’s infiltration theory (1933) has been developed for use in mathematical rainfall-runoff modelling which indicates that if the rainfall supply exceeds the infiltration capacity, infiltration tends to decrease in an exponential manner.

The Theis’s nonequilibrium equation (1935) introduced a groundbreaking tool for determining the hydraulic properties (transmissivity and storativity) of non-leaky confined aquifers. Analysis with the Theis method is performed by matching the Theis type curve to drawdown data plotted as a function of time on double logarithmic axes.

The use of extreme-value distributions for frequency analysis of hydrologic data which was proposed by Gumbel (1958) has served as the basis for modern statistical hydrology.

What agencies in the US made significant contributions in hydrologic theory and the development of a national network of gages for precipitation, evaporation, and stream flow measurements?

The U.S. Army Corps of Engineers (ACOE), the NWS within NOAA, the U.S. Department of Agriculture (USDA), and the USGS made significant contributions in hydrologic theory and the development of a national network of gages for precipitation, evaporation, and stream flow measurements.

The NWS is largely responsible for rainfall measurements, reporting and forecasting of severe storms, and other related hydrologic investigations. Meanwhile, the U.S. ACOE and the USDA Soil Conservation Service (now called the Natural Resources Conservation Service [NRCS]) made significant contributions to the field of hydrology in relation to flood control, reservoir development, irrigation, and soil conservation during this period.

Moreover, the USGS has taken significant strides to set up a national network of stream gages and rainfall gages for both quantity and quality data. Their water supply publications and special investigations have done much to advance the field of hydrology by presenting the analysis of complex hydrologic data to develop relationships and explain hydrologic processes. The NWS and USGS both support numerous websites for the dissemination of watershed information and precipitation and streamflow data from thousands of gages around the country.

Advancements in the Field of Hydrology for the following Period

1950s-1960s

During the 1950s to 1960s, the tremendous increase of urbanization following World War II in the United States and Europe led to better methods for predicting peak flows from floods, for understanding impacts from urban expansion, and for addressing variations in storage in water supply reservoirs. Water resource studies became an everyday occurrence in many rapidly developing areas of the United States, tied to the expansion of population centers in the southern, southwestern, and western states.

The decade of the 1960s witnessed the birth of computer revolution and hydrologic modeling took a giant leap forward. The computer provided the power for doing computations that was not available before. As a result, a new branch of hydrology, called digital or numerical hydrology, was born. Another branch that came into being was statistical or stochastic hydrology that often required analyses of large volumes of data.

1970s-1980s

In the 1970s and early 1980s, the evaluation and delineation of floodplain boundaries became a major function of hydrologists, as required by the Federal Emergency Management Agency (FEMA) and local flood control or drainage districts. In order for communities to be eligible for flood insurance administered by FEMA, they are required to delineate floodplain boundaries using hydrologic analysis and models. This function has taken on a vital role in many urban areas, as damages from severe floods and hurricanes continue to plague the United States, especially in coastal and low-lying areas.

In 1973, Mein and Larson developed a model for computing infiltration under steady rain. In 1975, Freeze presented a stochastic conceptual analysis of one-dimensional groundwater flow in nonuniform homogeneous media. In 1979, Gash developed an analytical model for infiltration loss by forests. The field of groundwater has since expanded dramatically.

1980s-1990s

In the 1980s, the simultaneous simulation of water flow and sediment and pollutant transport was undertaken; likewise, simultaneous simulation of different phases of flow, such as liquid and gaseous, was done (Bear and Verruijt 1987; Charbeneau 2000).

In 1987, Fok summarized developments in infiltration and its application. In 1990, Singh and Yu developed a generalized framework for infiltration and derived several popular infiltration models as special cases.

In the years that followed, computing prowess increased exponentially and hydrology began maturing and expanding in both depth (vertically) and breadth (horizontally). Tools from fluid mechanics, statistics, information theory, and mathematics were employed and became part of hydrology (Bras and Rodriguez-Iturbe 1985; Clarke 1998; Gelhar 1993; Mays and Tung 1992; Singh et al. 2007; Tung and Yen 2005). Furthermore, computer also made the development of user-friendly software possible , and tools for date acquisition, storage, retrieval, processing, and dissemination (Croley 1980; Hoggan 1989).

1990s-2020

In recent years, remote sensing tools, such as radar and satellites, came into being that made possible to acquire spatial data for large areas (Engman and Gurney 1991; Hogg et al. 2017; Lakshmi 2017; Lakshmi et al. 2015).

The development of the Stanford Watershed Model (Crawford and Linsley 1966) was followed by the umpteen watershed models that were developed all over the world (Singh 1995; Singh 2002 and Frevert 2006). The optimization or operations research techniques were also developed, which formed the basis for reservoir management and operation as well as river basin simulation. Some of these techniques were also used for calibrating hydrologic models (Beven 2001; Duan et al. 2003).

Moreover, two- and three-dimensional modeling was made possible because of advances in numerical mathematics. Consequently, two- and three-dimensional models of groundwater as well as of infiltration and soil water flow were developed (Bear 1979; Pinder and Celia 2006; Remson et al. 1971).

Another area that mushroomed subsequent to the pre-computer era is instrumentation. New instruments which were more accurate and sophisticated were developed for measuring all kinds of hydrologic variables, such as velocity, soil moisture, water and air quality parameters, fluxes in porous media, energy fluxes, and so on. Further, instrumentation for data transmission from place of measurement to place of storage, processing, storage, retrieval, and dissemination became highly robust and accessible (Liang et al. 2013; Sivakumar and Berndtsson 2010).

Computer Advances in Hydrology since 1960s to Present

The introduction of the digital computer into hydrology during the 1960s and 1970s allowed complex water problems to be simulated as complete systems for the first time. Large computer models can now be used to match historical data and help answer difficult hydrologic questions (Singh and Frevert, 2006).

Hydrologic computer models developed in the 1970s have been applied to areas previously unstudied or only empirically defined. For example, urban stormwater, floodplain and watershed hydrology, drainage design, reservoir design and operation, flood frequency analysis, and large-river basin management have all benefited from the application of computer models.

Single-event models such as HEC-HMS are used to simulate or calculate the resulting storm hydrograph (discharge vs. time) from a well-defined watershed area for a given pattern of rainfall intensity. Continuous models such as the Hydrological Simulation Program—Fortran (HSPF) and the Storm Water Management Model (SWMM) can account for soil moisture storage, evapotranspiration, and antecedent rainfall over long time periods. Statistical models can be used to generate a time series of rainfall or streamflow data, which can then be analyzed with flood frequency methods.

Newer distributed hydrologic models (i.e., VFLO and the MIKE series of models) can handle input, output, and data manipulation at the watershed level. Unquestionably new digital approaches combined with distributed terrain modeling have revolutionized hydrology in recent years, just as the original wave of models did in the decade of the 1970s. Also faster computers and available datasets have been instrumental in advancing the field.

The data revolution in hydrology and geographical information systems (GIS) have made available newer and more accurate datasets on topography, slope, rainfall, soils, land use, and channel characteristics for many areas. Moreover, most hydrological and meteorological data may be retrieved online from agencies such as the USGS and NWS, and various county and municipal sources. These datasets, combined with existing simulation models in hydrology, if applied correctly, provide the most accurate approach to understanding complex water resources systems, and a new era in the science of hydrology has begun this decade. New design and operating policies are being advanced and implemented that could not have been realized or tested before without the aid of sophisticated computer models linked with digital data.

References

Bedient, P. B., Huber, W. C., & Vieux, B. E. (n.d.). Hydrology and Floodplain Analysis (Vol. Fifth Edition). PEARSON. Retrieved August 2020

Bulu, A. (2010, May). Retrieved August 30, 2020, from hidropolitikakademi.org: https://www.hidropolitikakademi.org/uploads/wp/2019/01/Historical-Development-of-Hydrology.pdf

Charles Vernon Theis. (n.d.). Retrieved August 29, 2020, from http://www.aqtesolv.com/theis.htm

Singh, V. P. (2018). Springer Link. Retrieved August 30, 2020, from https://link.springer.com/article/10.1186/s40562-018-0113-z?fbclid=IwAR2LMq1UAFcimg0Qbl6yaw1xJmRDinAppEou_6CUt2IO8uOp90s-MU7n440

Unit Hydrograph – Advanced Hydrology. (n.d.). Retrieved August 31, 2020, from https://nptel.ac.in/content/storage2/courses/105101002/downloads/module3/lecture4.pdf