Chandra S. Pathak's research while affiliated with US Army Corps of Engineers and other places

Publications (70)

Article
en A changing climate leads to changes in the frequency, intensity, spatial extent, duration and timing of weather and climate extremes, and can result in unprecedented extremes. These climate extremes have significant impacts on human and ecological systems, which are influenced by changes in climate, vulnerability and exposure, resulting in incre...
Article
Full-text available
Evaluating trends of historical rainfall and lawn water demand on a weekly and seasonal basis is needed for optimizing lawn and landscape water conservation policy. Outdoor water restrictions are a common conservation strategy and typically feature a “day of the week” schedule to limit the frequency and duration of urban lawn water use. However, ou...
Article
Variants of spatial interpolation and data-driven methods to fill gaps in daily precipitation records are developed and evaluated in this study. The evaluated methods include variations of inverse distance and correlation weighting procedures, linear weight optimization and artificial neural networks. An already existing method, support vector logi...
Article
Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.
Article
A methodology for optimal ground-based sensor network design for an evapotranspiration (ET) estimation method which uses solar radiation as the only parameter is developed and evaluated in this study. The methodology employs geospatial analyses and a geostatistical approach, and data from ground-based sensors and satellite-based estimates of solar...
Article
A geostatistical method was applied to optimize an existing groundwater-level monitoring network in the Upper Floridan aquifer for the South Florida Water Management District in the southeastern United States. Analyses were performed to determine suitable numbers and locations of monitoring wells that will provide equivalent or better quality groun...
Article
Correcting real-time radar-rainfall estimates for mean field systematic errors (bias) is normally accomplished through gauge-based adjustment procedures. This study explores two auxiliary data sources derived from cloud-to-ground (CG) lightning measurements and storm tracking applied on radar images in terms of providing microphysical information u...
Conference Paper
A groundwater-level monitoring network was designed for the Upper Floridan aquifer in southern Florida, U.S.A., within the boundaries of the South Florida Water Management District. The objective of the investigation was to design a groundwater monitoring network for the Upper Floridan aquifer that recommends the number and locations of monitoring...
Conference Paper
Watershed run-off models were mostly developed using point rainfall observations in the past. For several decisions making, water quality model using watershed run-off models. The water quality modeling can be done in a better manner if radar rainfall data is used in the modeling process. However, radar rainfall is not directly available for this p...
Conference Paper
Accurate measurement of climate variables via the optimal number and location of ground sensors is important to accurately compute evapotranspiration over a large area. Optimal ground sensor networks for each of the four evapotranspiration (ET) parameters (solar radiation, air temperature, relative humidity, and wind speed) were developed independe...
Conference Paper
Bias corrections of radar data using ground truth is essential and critical step in generation of viable precipitation data sets. The improvement in the radar data achieved through the correction procedures depend on several factors including available rain gage data, gage density and reliability of ground truth. Availability of rain gage data at t...
Article
Geo-spatial interpolation methods are often necessary in instances where the precipitation estimates available from multisensor source data on a specific spatial grid need to be transformed to another grid with a different spatial grid or orientation. The study involves development and evaluation of spatial interpolation or weighting methods for tr...
Article
Use of appropriate functional reflectivity (Z)-rainfall rate (R) relationships is crucial for accurate estimation of precipitation amounts using radar. The spatial and temporal variability of several storm patterns combined with subjectivity in application of a specific functional Z-R relationship for a particular storm makes this task very difficu...
Article
Radar-based hydrological prediction relies on available raingauges to correct for bias in rainfall estimates. Standard Z-R (radar reflectivity factor against rain-rate) relationships have been developed which are characteristic of storm types, e.g. convective or tropical storms. However, the evolution of storm drop-size distribution and radar-speci...
Conference Paper
Accurate measurement of climate variables via the optimal number and location of ground sensors is important to accurately compute evapotranspiration over a large area. The goal of this project was to develop an optimal ground sensor network for the climate variable - wind speed for the South Florida Water Management District (SFWMD) using the avai...
Conference Paper
Distributed rainfall information is necessary for making operational hydrologic predictions and for retrospective studies. Rainfall measurements from radar require conversion of reflectivity into rainfall rates, but are known to contain systematic errors, or bias. This uncertainty can limit the utility of radar rainfall. Quality control and enhance...
Article
Albedo was monitored over a two-year period (beginning April 2008) at three forested wetland sites in Florida, USA using up- and down-ward facing pyranometers. Water level, above and below land surface, is the primary control on the temporal variability of daily albedo. Relatively low reflectivity of water accounts for the observed reductions in al...
Article
Assessment of long-term trends in extreme precipitation data is critical for hydrologic design. Understanding of such trends is also essential from a climate change perspective and requires an extensive evaluation of trends in different temporal slices of historical precipitation data series. The current study focuses on evaluation of these trends...
Article
Accurate gauge corrected radar rainfall predictions are necessary for making operational hydrologic predictions. Radar rainfall estimates derived from conversion of reflectivity are known to contain systematic errors, or bias, and other random errors or artifacts that can limit the utility of radar rainfall. Quality control and enhancement of radar...
Article
Albedo was monitored over a two-year period (beginning on April 11, 2008) at three forested wetland sites in Florida, USA using up- and down-ward facing pyranometers. Water level, above and below land surface, is the primary control on the temporal variability of albedo and the relatively low albedo of water accounts for the observed reductions in...
Conference Paper
Uncertainty assessment of hydrologic model inputs and outputs is generally achieved by using Monte Carlo perturbation schemes adopted for specific input parameters. Several variants of perturbation schemes ranging from simple random sampling to Latin-hypercube sampling schemes are used in hydrologic modeling for uncertainty estimation purposes. Thi...
Conference Paper
In the current study the use of optimal spatial interpolation and data driven models for infilling of rain gage data using NEXRAD based precipitation estimates is investigated. A total of 12 optimization model formulations were proposed, developed and were implemented in this study. The optimization models were developed using nonlinear and mixed i...
Conference Paper
Radar-based hydrologic prediction relies on available rain gauges to correct for bias in rainfall estimates. Standard Z-R relationships have been developed, which are characteristic of storm types, e.g. convective or tropical storms. However, the evolution of storm drop size distribution and radar-specific factors can affect the accuracy of these s...
Article
Robust hydrologic monitoring networks represent a critical element of decision support systems for effective water resource planning and management. Moreover, process representation within hydrologic simulation models is steadily improving, while at the same time computational costs are decreasing due to, for instance, readily available high perfor...
Article
Uncertainty assessment of hydrologic model inputs and outputs is generally achieved by using Monte Carlo perturbation schemes adopted for specific input parameters. Several variants of perturbation schemes ranging from simple random sampling to Latin-hypercube sampling schemes are used in hydrologic modeling for uncertainty estimation purposes. Thi...
Article
Accurate radar rainfall predictions are necessary for making operational hydrologic decisions even when gauge correction is not available. Many standard Z-R relationships have been developed for estimating rainfall however, it has been found that seasonally and spatially specific Z-R relationships may lead to improved precipitation estimates. The p...
Article
Use of appropriate reflectivity (Z)-rain rate(R) relationships is crucial for accurate estimation of precipitation amounts using radar. The spatial and temporal variability of several storm patterns combined with availability of several variants of Z-R relationships makes this task very difficult. This study evaluates the use of optimization models...
Article
Paech, Simon J., John R. Mecikalski, David M. Sumner, Chandra S. Pathak, Quinlong Wu, Shafiqul Islam, and Taiye Sangoyomi, 2009. A Calibrated, High-Resolution GOES Satellite Solar Insolation Product for a Climatology of Florida Evapotranspiration. Journal of the American Water Resources Association (JAWRA) 45(6):1328-1342. Abstract: Estimates of in...
Conference Paper
Historical rainfall records are of extreme importance to most hydrologic analyses, including water resources evaluation, impact of land use changes, urban runoff volumes and durations, hydro periods, flood analyses, climate variability, among many others. However, daily precipitation records are rarely complete and suffer from occasional and extend...
Conference Paper
Temporal water budget assessments are necessary for short- and long-term water resources management and operational planning. However, these estimates are subject to a variety of potential sources of error, some of which are not easily quantifiable. Several past water budget studies have focused on quantifying residual errors and improving the wate...
Conference Paper
Climatologically homogeneous rainfall regions were developed for the South Florida Water Management District (District) using statistical techniques in conjunction with physical meteorological processes. Rain gauge adjusted NEXRAD (radar) derived rainfall datasets were prepared and stored in the Florida State University (FSU) MPE database. The vari...
Conference Paper
Accurate measurement of solar radiation via optimal number of ground sensors and their respective location is important to estimate evapotranspiration (ET). One way of estimating ET on regional scales at high spatial resolution (∼2 km) on daily time scales is through the use of GOES Satellite solar radiation data. The goal of this study is to perfo...
Conference Paper
Radar rainfall estimates derived from conversion of reflectivity are known to contain systematic and random errors (bias) that limit the quantitative use of radar rainfall in various applications. Enhancement of radar rainfall estimates is normally accomplished through gauge-adjustment procedures; however, those procedures require long integration...
Article
Full-text available
The South Florida Water Management District (SFWMD) relies on a network of nearly 300 rain gauges in order to provide rainfall data for use in operations, modeling, water supply planning, and environmental projects. However, the prevalence of convective and tropical disturbances in South Florida during the wet season presents a challenge in that th...
Article
Accurate rainfall information across a wide range of space and time scales is needed to support water management decisions in Florida. The Florida Water Management Districts are regional governmental agencies with water quality, flood control, water supply and environmental restoration responsibilities. Statewide rainfall at high resolution is prod...
Article
Geo-spatial interpolation methods are often necessary in instances where the precipitation estimates available from multi-sensor or NEXRAD for a specific spatial grid needs to be transformed to another grid with a different spatial grid or orientation. The study current focuses on development, evaluation and implementation of spatial interpolation...
Article
The availability of accurate precipitation data is essential for hydrologic modeling and water resources management. Recent advances NEXRAD and satellite based measurements have provided alternative methods for precipitation estimation. The current study focuses on comparative evaluation and assessment of TRMM (Tropical Rainfall Measuring Mission)...
Conference Paper
Solar radiation data are critically important for the estimation of evapotranspiration. Analysis of visible-channel data derived from Geostationary Operational Environmental Satellites (GOES) using radiative transfer modeling has been used to produce spatially- and temporally-distributed datasets of solar radiation. An extensive network of (pyranom...
Conference Paper
The South Florida Water Management District (District) is responsible for managing water resources in 16-counties over a 46,439-square kilometer (17,930 square-mile) area. The area extends from Orlando to Key West and from the Gulf Coast to the Atlantic Ocean and contains the country's second largest lake - Lake Okeechobee and the world famous Ever...
Conference Paper
The South Florida Water Management District (District) is responsible for managing water resources in 16-counties over a 46,439-square kilometer (17,930 square-mile) area. The area extends from Orlando to Key West and from the Gulf Coast to the Atlantic Ocean and contains the country's second largest lake - Lake Okeechobee and the world famous Ever...
Conference Paper
The South Florida Water Management District (District) is responsible for managing water resources in 16-counties over a 46,439-square kilometer (17,930 square-mile) area. The District's area extends from Orlando to Key West and from the Gulf of Mexico to the Atlantic Ocean and contains the country's second largest freshwater lake, Lake Okeechobee,...
Conference Paper
Deterministic and stochastic weighting methods are the most frequently used methods for infilling rainfall values at a gage based on values recorded at all other available recording gages or other sources. Radar (NEXRAD) data is also commonly used for infilling of rainfall data. Several issues that affect the infilling methods include: the historic...
Conference Paper
The use of radar (NEXRAD) estimated rainfall data for providing information about the extreme rainfall amounts resulting from storms, hurricanes and tropical depressions is common today. Often corrections are applied to the RADAR generated rainfall data-based on what was actually measured on the ground by rain gages. Understanding and modeling the...
Conference Paper
The hallmark of recent advances in radar precipitation estimates is the high resolution detection of spatially variable rainfall over large areas. Radar data far exceeds spatial densities of most rain gage networks and is useful for filling in the gaps between gage measurements. While radar provides the spatial and temporal patterns of rainfall, it...
Article
Two widely used procedures for optimally combining radar- and gauge-derived rainfall are those of the OneRain Corporation and the National Weather Service (NWS). The NWS procedure, called the Multi-sensor Precipitation Estimator (MPE), produces an hourly product on the 4×4 km Hydrologic Rainfall Analysis Project (HRAP) grid. MPE is used operational...
Article
Motivation for this study comes from the South Florida Water Management District (District) who is responsible for managing water resources in 16-counties over a 46,439-square kilometer (17,930 square-mile) area. Near-real- time rainfall data are used in operation of approximately 3,000 kilometers (~1,800 miles) of canals, 22 major pump stations an...
Article
The use of radar (NEXRAD) estimated rainfall data for providing information about the extreme rainfall amounts resulting from storms, hurricanes and tropical depressions is common today. Often corrections are applied to the RADAR-based rainfall data-based on what was actually measured on the ground by rain gages. Understanding and modeling the rela...
Article
The ecological and physical characteristics of South Florida have been shaped by years of hydrologic variation. South Florida hydrology is driven by continuous balance of rainfall and evapotranspiration reflected in surface water runoff, surface and subsurface storage, flows through the low relief features, dry-outs and wildfires. Generally, the re...
Article
The South Florida Water Management District (District) currently operates 6 Stormwater Treatment Areas (STAs) located in the Everglades Agricultural Area (EAA) covering a total of 16,200 hectares. STAs are large wetland filter marshes that receive agricultural runoff in an effort to reduce suspended solids and nutrients prior to discharge to enviro...
Article
Two widely used procedures for optimally combining rada r- and gauge - derived rainfall are those by the OneRain Corporation and the National Weather Service (NWS). This paper statistical ly compar es values from the two schemes. We consider the area of the South Florida Water Management District (SFWMD) d uring the 2005 calendar year . Comparison...
Conference Paper
Full-text available
The distribution of rainfall in space and time measured by a rain gauge network is a critical element in the management of precious water resources, whether the network is used alone or in combination with weather radar. In 2004, the District initiated a program to optimize the rain gauge network for purposes of near-real time and end of month adju...
Conference Paper
The intent of this paper is to examine a rain gauge based adjustment technique for basin averaged daily radar-rainfall field estimates on the basis of on-line rainfall measurements from rain gauges located in the Upper and Lower Kissimmee River Basins in South Florida. The rainfall estimates are derived from two radar rainfall algorithms applied on...
Article
Full-text available
The South Florida Water Management District (SFWMD) is an agency that relies on a network of nearly 300 rain gauges in order to provide rainfall data for use in operations, modeling, water supply planning, and environmental projects. However, the prevalence of convective and tropical rainfall events in South Florida during the wet season presents a...
Conference Paper
The South Florida Water Management District (District) is responsible for managing water resources in 16 counties over a 46,439-square kilometer (17,930 square-mile) area. The area extends from Orlando to Key West and from the Gulf Coast to the Atlantic Ocean and contains the second largest freshwater lake that is wholly within the United States —...
Conference Paper
The South Florida Water Management District (District) is responsible for managing water resources in 16-counties over a 46,439-square kilometer (17,930 square-mile) area. The area extends from Orlando to Key West and from the Gulf Coast to the Atlantic Ocean and contains the country's second largest lake — Lake Okeechobee and the world famous Ever...
Conference Paper
Achieving optimal use of an existing hydrological monitoring network requires a system-wide optimization study. To minimize operational requirements, an optimized stage monitoring network should employ the fewest number of stations positioned in strategic locations. The South Florida Water Management District (SFWMD) oversees several hydraulic/hydr...
Conference Paper
The South Florida Water Management District collects, validates, and archives hydrometeorological data that includes rainfall, water level (stage), water control structure operations, flow and others. A pilot project was undertaken to enhance stage-monitoring network for a portion of the remnant Everglades of south Florida. This paper details the m...
Conference Paper
The South Florida Water Management District is responsible for managing water resources in a 46,439 square-kilometer (17,930 square-mile) region. The area extends from Orlando to Key West and from the Gulf Coast to the Atlantic Ocean and contains the country’s second largest lake. The area is also the site of a major environmental restoration proje...

Citations

... Among the different probability distributions in the past studies [44,[55][56][57][58], Generalized Extreme Value (GEV) was considered as a more efficient and better fit for the streamflow distribution. GEV is also used as a statistical best fit distribution to predict future extremes, especially hydroclimatic extremes by several researchers [55,59]. ...
... Ensuring a reliable and sustainable water supply through effective water resource planning, depends on our ability to understand hydrological flows and their variability into the future [6,7]. The progression of anthropogenic climate change and extreme weather events hinders our ability to accurately predict changes in the hydrological system response [8]. ...
... The findings of this paper can apply to both golf course roughs and home lawns because of similar management practices. Furthermore, policymakers may conserve more water during prolonged droughts by restricting irrigation of Meyer to 20-30% ET o rather than imposing traditional restrictions, especially for high irrigators (Boyer et al., 2018;Survis et al., 2017). ...
... Studies by Teegavarapu and Chandramouli [48] and Teegavarapu et al [49] provided several alternatives to IDW methods. Teegavarapu et al [50] used connotation rules within weighting methods to improve estimates of missing precipitation data. Global estimation methods that use trend and regression analysis are also applicable for spatial interpolation. ...
... Even though radar rainfall data in many cases are available on web, their use with quality control/assurance and bias correction is recommended. Pathak et al. (2017) edited a special issue of Journal of Hydrologic Engineering on radar rainfall and operational hydrology that contains papers dealing with radar rainfall data estimation, improvement, and validation; application of radar rainfall data; and use of radar rainfall for flood forecasting. ...
... As hydrologic-hydraulic models for urban flood modeling are critical to flood prediction, infrastructure design, and adaptation planning, it is crucial to also understand the impact of different sources of error and uncertainty (Pathak et al., 2015). For engineers and planners developing asset management plans (Harvey et al., 2017), designing flood mitigation infrastructure (Kabisch et al., 2017;Kuriqi and Hysa, 2021) or rehabilitating drainage structures (Martínez et al., 2018), accurate hydraulic information of the drainage system as well as communication of output uncertainty is vital. ...
... The insolation model runs in the computational environment of the Man-computer Interactive Data Access System (McIDAS [39]), developed and distributed by the SSEC. Near-real-time insolation fields from this system have been used for regional-and continental-scale land surface carbon and water flux assessments [5,26,[40][41][42], solar energy spatial and temporal variability analyses [43], subsurface hydrologic modeling efforts, and currently for agricultural forecasting products from the University of Wisconsin-Madison Extension (Madison, WI, USA) [44]. ...
... These benefits, however, come at a price, since they are subject to quantitate errors [4]. There is a large number of factors that affect the quality of the QPE, such as systematic errors due to improper calibration of the rainscanner system, signal attenuation issues and the use of a proper radar reflectivity, Z, to rainfall intensity, R relationship, also known as Z-R relationship, among others [5]. The Z-R relationship is among the most crucial parameters to be configured since it transforms the measured reflectivity fields, Z (mm 6 /m 3 ), to rainfall intensity, R (mm/h). ...
... Steiner and Smith (2000) studied the uncertainty inherent in the estimation of one parameter from the other in traditional Z − R relationships caused by the natural variability of DSD within and between storms. Anagnostou et al. (2013) proposed the use of cloud-to-ground lightning information and a storm-tracking algorithm for distinguishing different storm types. The MFB was then evaluated and corrected for different storm types using a ratio of the gauge estimate to the radar estimate. ...
... The SFWMD maintains a contract with a vendor to obtain data at a spatial resolution of 2 km × 2 km. The end-of-month radar estimates available through SFWMD are run through a QA/QC process that includes using algorithms to adjust radar estimates to rain gauge data [29,30]. ...