Search

Sedimentation is one of the most important factors affecting stream channel stability. A proposed model was developed to estimate the sediment load of an artificial channel by the integrati...

The loss of topsoil in the United States has resulted in low crop yield, reduction of reservoir capacity, cost increase of water treatment, and detrimental effects on aquatic life and wildlife habitats. An initial step for taking conservation measures in any watershed is to identify locations where erosion protection measures are needed. Applying the Revised Universal Soil Loss Equation (RUSLE) and a geographic information system (GIS), this study attempts to locate the most erodible locations, namely erosion hotspots, for a watershed. Using GIS, the watershed is divided into 25×25-m grids and the RUSLE, including rainfall-runoff erosivity factor, soil erodibility factor, combined slope length and slope steepness factor, cover management factor, and support practice factor, is applied for the estimation of soil erosion potential for each grid cell. By ranking these grid values of erosion potential in a descending order, the top 1% and corresponding locations are defined as the erosion hot spots, w...

Soil erosion, more than any other factor, has more significant and direct impacts on a hydrological watershed in terms of environmental problems. After deriving the erosion hotspots, this s...

Most economic developments may have been at the expense of soil conservation. Soil erosion results in impacts on reservoir sediment, crop yield, and water quality. This study introduces the procedure of using a geographical information system for investigating reservoir sediments and soil erosion of the corresponding watershed. First, the bathymetric surface of a reservoir is surveyed using two real-time kinematic global position systems and a sonar-based depth gauge. Using the on-board computer, receivers, and sonar, bathymetric readings are recorded three times a second to establish actual coordinates and depth measurements. Data are then converted using a digital terrain model to obtain the current image bathymetric surface. The image of original bathymetric surfaces when constructed can be obtained by digitizing the existing map. The subtraction of these two images is used to estimate the amount of sediment deposits. Next, parameters of rainfall-runoff erosivity factor, soil erodibility factor, slope length factor, slope steepness factor, cover-management factor, and support practice factor are evaluated for each grid of the corresponding watershed. The average annual soil loss from each grid is estimated by the revised universal soil loss equation to obtain the total amount of the soil loss for the watershed. Using the example of Charles Mill Lake, Ohio, USA, the estimated average amount of sediment deposits in the lake was about 2.44 x 10 4 m 3 year -1 . On the other hand, the estimated soil erosion from the corresponding watershed was about 4.22 x 10 8 kg year -1 or 1.56 x 10 5 m 3 year -1 . Hence, it can be concluded that about 15.6% of the soils eroded from the watershed have been deposited in the lake.

Soil erosion has resulted in many environmental problems in the United States. This study is to define watershed erosion hotspots and compare them in the two watersheds in Ohio. The watershed is divided into 30×30 m grids using Geographic Information System (GIS) while the Revised Universal Soil Loss Equation (RUSLE) is applied to estimate the soil erosion potential for each grid. Based the applications to Hocking River Basin and Atwood Lake Basin in Ohio, it is found that the hotspot erosion rates are 0.282 kg/m 2 /year and 0.164 kg/m 2 /year, respectively. After identifying the most erodible locations, comparison of effects of individual factor between the two watersheds are investigated. The correlation analysis indicates that land uses significantly influence the soil erosion of each watershed while soil types have limited effect. The highest average erosion rate occurs in barren lands. Developed medium and high intensity areas also have high erosion potentials. Based on the classification of geologic soil types, soil types with the highest erosion potentials are LoC, GIG and BtF at the Hocking River Basin, while the ones of the Atwood Lake Basin are ChB, CoB and FdA. Topography is the dominant factor for both the two basins.

A regional water conservation system for drought management involves many uncertain factors. Water received from precipitation may stay on the ground surface, evaporate back into the atmosphere, or infiltrate into the ground. Reliable estimates of the amount of evapotranspiration and infiltration are not available for a large basin, especially during periods of drought. By applying a geographic information system, this study develops procedures to investigate spatial variations of unavailable water for given levels of drought severity. Levels of drought severity are defined by truncated values of monthly precipitation and daily streamflow to reflect levels of water availability. The greater the truncation level, the lower the precipitation or streamflow. Truncation levels of monthly precipitation are recorded in depth of water while those of daily streamflow are converted into monthly equivalent water depths. Truncation levels of precipitation and streamflow treated as regionalized variables are spatially interpolated by the unbiased minimum variance estimation. The interpolated results are vector values of precipitation and streamflow at a grid of points covering the studied basin. They are then converted into raster-based values and expressed graphically. The image subtraction operation is used to subtract the image of streamflow from that of precipitation at their corresponding level of drought severity. It is done on a cell-by-cell basis resulting in new attribute values to form the spatial image representing a spatial distribution of potential water loss at a given level of drought severity.

The flood frequency analysis has been widely conducted where gauging stations are available and statistical distributions can be used to analyze historical data. On the other hand, flash floods usually occur at unexpected locations having no gauging stations, and have hardly been discussed. Based on the available information from surrounding precipitation gauges, potential flash floods were defined for a watershed and their regional distributions were investigated. Daily truncation levels of 99.9 and 99.99% were used to derive potential flash floods, where a 99.9% level means that 0.1% of daily precipitations are larger than or equal to the truncated value. The higher the truncation level, the greater the magnitude of a potential flash flood. Records from 21 precipitation gauging stations were selected for the studied region. The kriging method based on the minimum variance unbiased estimation was introduced to calculate spatial interpolation. These kriging estimates form a regional distribution of potent...

A daily drought-monitoring system was developed using the Clips Expert System software package. The monitoring system consists of four components: (1) the knowledge base, which contains rules in th...

Ground water drought events were derived by taking a truncation level through the time series of daily ground water depth that are recorded elevation differences between the water table and land surface at a well site. Droughts of various truncation levels at 70, 80, 90, and 95 percent, were obtained, where a 70 percent truncation level means that 70 percent of ground water depth data are less than or equal to the truncated value. The conditional probability that a drought occurring at a certain truncation level will prolong and advance to that of the next higher level was estimated. The regionalization analysis was conducted assuming that conditional probabilities estimated at selected wells are regionalized variables. Contour lines of conditional probabilities for each truncation level were constructed to express their spatial variability in the region. Estimation errors associated with the regionalization were reasonably small.

During periods of drought, an important goal of water-resource management is the establishment of realistic reservoir operating policies for water allocation, especially for a river system involved with flood-control reservoirs. This paper discusses optimization models for the flood-control reservoir operations at varied levels of drought severity. It is assumed that for a certain drought-severity level, there will be corresponding minimum demands at downstream control points and maximum inflows to reservoirs. A constant reservoir yield was estimated for each reservoir, based on the maximum duration of historic drought events on the 70% truncation level. Based on the drought evaluation, optimization models at the 70%, 80%, 90%, and 95% levels of drought severity were developed and applied to a river system involved with four flood-control reservoirs in the Scioto River Basin in central Ohio.

This study is to design and develop a sustainable virtual boat integrated with lesson plans for water resource and environmental education. The virtual boat, designed based on the Unity 3D platform, is built to simulate a physical boat used for water sampling along the Ohio River from Marietta to Gallipolis, Ohio. Two lesson plans, water quality index and pollution locator GPS (Global Position System), are developed that students can navigate the virtual boat along the Ohio River conducting water sampling activities and exploring water pollution problems similar to those in a physical boat. The effectiveness and usability of the developed model were assessed in the two local high school science classrooms. The result shows that the developed model is a promising tool for water resources and environmental education.

Precipitation droughts were defined using monthly precipitation time series and different truncation levels—namely, 70%, 80%, 90%, and 95%—in which a 70% truncation level means that 70% of the recorded monthly precipitations are greater than or equal to the value. Conditional probabilities that droughts of certain truncation levels will advance to their next higher levels were estimated at each gage location. There are 21 precipitation stations selected in the Scioto River Basin, in Ohio, for the study of regional drought characteristics. The kriging method based on the minimum unbiased estimation was used to obtain a regional distribution of conditional drought probabilities at each truncated level. Contour lines of conditional probabilities for each truncation level were constructed to show possible drought‐prone distributions for the ungaged region. This reflects the areal severity of water shortage in case of drought.

Existing definitions of drought have focused on limited hydrologic indicators and are less effective for the purpose of drought monitoring. This study uses historical records of streamflow, precipitation, ground water, temperature, and lake elevation to define drought. Based on the method of truncation, drought durations and conditional probabilities of each indicator were estimated to define the drought severity levels, namely, 70 percent, 80 percent, 90 percent, and 95 percent. A drought monitoring method was developed by a combination of truncation level, duration, and conditional probabilities of five indicators. A six-month period of the 1988 drought in the central Ohio region was used to test the monitoring method. It was found that the developed method could effectively detect an occurrence of drought.

The concept of recurrence interval has been used for years in engineering designs. Can the same concept be applied to the drought analysis? This paper uses the plotting position method to define drought of various recurrence intervals based on stream-flow data. The method of truncation level was applied to the same data to examine the defined drought. Based on the method of truncation level, drought duration and its corresponding flow deficit were investigated. Eighteen flow gage stations from the Scioto River Basin in Ohio were selected for the study. The results show that flows of 100-year droughts using the plotting position method are practically nil. On the other hand, flows of droughts using the truncation method are gradually decreasing with an increase in truncation level, where flows of 95 percent are approximately equal to those of two-year droughts defined by the plotting position. It is also shown that there is a strung correlation between drought duration and deficit.

Droughts are defined using daily streamflow series and different truncation levels including 30%, 50%, 60%, 70%, 80%, and 90% of recorded daily flows. Flow ratios, which are obtained by dividing subbasin flows of different truncation levels by their corresponding outlet flows, are calculated. It is found that the flow ratios of 17 selected subbasins decrease significantly with increasing truncation levels while their mean‐flow ratios are approximately equal to their corresponding area ratios. Therefore, the estimation of irrigation water using the drainage area ratio, which has been practiced in the studied drainage basin, is impractical in case of droughts. Furthermore, assuming the time‐dependent Poissonian behavior of drought series, the drought intensity function was developed to investigate drought severity in the basin. Based on plots of drought intensity function, it is found that the drought intensity has been increasing significantly for the basin investigated.

The paper reviews a study that conducted an investigation into the use of pipeline selection for determining the deposit location of dredged materials by geographic information system (GIS). The criterion of pipeline length was used to determine the best wetland location. The paper summarizes the methodology that was developed using a pairwise comparison to determine the pipeline lenght to be the second most important criterion in selecting the disposal location for wetland formation.

For a small rural community situated on a flood plain, it is not economically justified for any flood protective structures. A community warning system by the use of existing precipitation gage stations could be an alternative. This paper investigated the regional distribution of potential flash floods based on several existing precipitation gages in the studied area. Daily truncation levels of 99.9 and 99.99% were used to derive potential flash floods, where a 99.9% level means that 0.1% of historically recorded daily precipitation are larger than or equal to the truncated value. The higher the truncation level, the more severe the potential flash flood. Daily precipitation records from twenty-one gages in the Scioto River Basin were selected for the study. The kriging method based on the minimum unbiased estimation was used to estimate spatial interpolation for ungaged areas. These estimations will form the regional distribution of potential flash floods at various truncation levels. Contour lines of these potential flash floods at each truncation level were constructed and associated errors were estimated. The result shows that estimation errors associated with constructed contour lines were reasonably small.

For the purpose of irrigation and water resources planning, it is important to know the water loss for a drainage basin. Unfortunately individual measurements of elements of the total water loss are not realistic, at least for the large watersheds studied in this research. Based on the water budget approach, annual water loss series are formulated in this paper. A modeling technique that includes the homogeneity test of data and the best model selection is developed to fit the water loss series by a stochastic process. The results of this study reveal the existence of data nonhomogeneities in the annual water loss series from the Ohio River Basin, which requires adjustments before the mode! fitting by a stochastic process. The selected best model by the criterion of the parsimony of parameter was successfully used to forecast the regional water losses based on the proposed procedure.

Records of extreme precipitation were investigated using the Discrete Autoregressive Moving Average (DABMA) process, which can explain long persistences of wet and dry spells that exist in daily precipitation data. The results show that the daily precipitation with strong autocorrelation is inclined to be better fit by a Discrete Autoregressive (DAB) model. On the other hand, those data with weak autocorrelations tend to be best fit by a Discrete Moving Average (DMA) model. It can also be concluded that based on the records from extremely wet and dry regions there is no geographic preference regarding the selection of the best model.

Flood series including three components, namely, the occurrence time, the discharge volume, and the flood duration, are formed from observed daily streamflows. The intensity function describing the flood occurrence rate is derived assuming the nonhomogeneous Poisson process. A fitted equation is applied to the estimated intensities by the least squares method. The Thinning method based on controlled deletion of points in a poisson process uses the fitted intensity function to generate the flood occurrence times which are expressed by a sequence of time intervals. The procedure of the marked point process is introduced to link the flood duration and the discharge volume, which are modeled, respectively, by exponential distributions, of the flood occurrence time. Therefore the simulated result consists of three-component flood series including the occurrence time, the flood duration and the discharge volume, which can be used for environmental pollution protection and flood-control purposes. The statistical comparisons made between the generated and the observed series are reasonably agreeable.