GENERALIZED LOW-FLOW FREQUENCY RELATIONSHIPS FOR UNGAGED SITES IN MASSACHUSETTS1

ABSTRACT: Regional hydrologic procedures such as generalized least squares regression and streamflow record augmentation have been advocated for obtaining estimates of both flood-flow and low-flow statistics at ungaged sites. While such procedures are extremely useful in regional flood-flow studies, no evaluation of their merit in regional low-flow estimation has been made using actual streamflow data. This study develops generalized regional regression equations for estimating the d-day, T-year low-flow discharge, Q_{d, t}, at ungaged sites in Massachusetts where d = 3, 7, 14, and 30 days. A two-parameter lognormal distribution is fit to sequences of annual minimum d-day low-flows and the estimated parameters of the lognormal distribution are then related to two drainage basin characteristics: drainage area and relief. The resulting models are general, simple to use, and about as precise as most previous models that only provide estimates of a single statistic such as Q_7,10. Comparisons are provided of the impact of using ordinary least squares regression, generalized least squares regression, and streamflow record augmentation procedures to fit regional low-flow frequency models in Massachusetts.     

EFFECTS OF BASIN-SCALE TIMBER HARVEST ON WATER YIELD AND PEAK STREAMFLOW1

ABSTRACT: Streamflow changes resulting from clearcut harvest of lodgepole pine (Pinus contorta) on a 2145 hectare drainage basin are evaluated by the paired watershed technique. Thirty years of continuous daily streamflow records were used in the analysis, including 10 pre-harvest and 20 post-harvest years of data. Regression analysis was used to estimate the effects of timber harvest on annual water yield and annual peak discharge. Removal of 14 million board feet of lodgepole pine (Pinus contorta) from about 526 hectares (25 percent of the basin) produced an average of 14.7 cm additional water yield per year, or an increase of 52 percent. Mean annual daily maximum discharge also increased by 1.6 cubic meters per second or 66 percent. Increases occurred primarily during the period of May through August with little or no change in wintertime streamflows. Results suggest that clearcutting conifers in relatively large watersheds (> 2000 ha) may produce significant increases in water yield and flooding. Implications of altered streamflow regimes are important for assessing the future ecological integrity of stream ecosystems subject to large-scale timber harvest and other disturbances that remove a substantial proportion of the forest cover.     

PREDICTION OF TWO-YEAR PEAK STREAM-DISCHARGES USING NEURAL NETWORKS1

ABSTRACT: The cascade correlation neural network was used to predict the two-year peak discharge (Q₂) for major regional river basins of the continental United States (US). Watersheds ranged in size by four orders of magnitude. Results of the neural network predictions ranged from correlations of 0.73 for 104 test data in the Souris-Red Rainy river basin to 0.95 for 141 test data in California. These results are improvements over previous multilinear regressions involving more variables that showed correlations ranging from 0.26 to 0.94. Results are presented for neural networks trained and tested on drainage area, average annual precipitation, and mean basin elevation. A neural network trained on regional scale data in the Texas Gulf was comparable to previous estimates of Q₂ by regression. Our research shows Q₂ was difficult to predict for the Souris-Red Rainy, Missouri, and Rio Grande river basins compared to the rest of the US, and acceptable predictions could be made using only mean basin elevation and drainage areas of watersheds.     

TREE-RING RECONSTRUCTION OF UPPER GILA RWER DISCHARGE1

ABSTRACT: Effective planning for use of water resources requires accurate information on hydrologic variability induced by climatic fluctuations. Tree-ring analysis is one method of extending our knowledge of hydrologic variability beyond the relatively short period covered by gaged streamflow records. In this paper, a network of recently developed tree-ring chronologies is used to reconstruct annual river discharge in the upper Gila River drainage in southeastern Arizona and southwestern Arizona since A.D. 1663. The need for data on hydrologic variability for this semi-arid basin is accentuated because water supply is inadequate to meet current demand. A reconstruction based on multiple linear regression (R²=0.66) indicates that 20th century is unusual for clustering of high-discharge years (early 1900s), severity of multiyear drought (1950s), and amplification of low-frequency discharge variations. Periods of low discharge recur at irregular intervals averaging about 20 years. Comparison with other tree-ring reconstructions shows that these low-flow periods are synchronous from the Gila Basin to the southern part of the Upper Colorado River Basin.     

Analysis of Appropriate Timescales for Water Diversion Permits in Brazil

Agreement on the criteria for granting the right to use water resources between governing bodies represents a significant advance in the process of sharing water use. To aid water resource management agencies in optimizing water use, the impact of using different criteria for permitting water use in the Paracatu river basin, Brazil, was evaluated in this study. The streamflow criteria corresponding to 30 % of the annual Q_7,10 (used by the governing body of Minas Gerais), 70 % of the annual Q₉₅ (used by the governing body of the union), 30 % of the monthly Q_7,10, and 70 % of the monthly Q₉₅ were evaluated. The use of criteria based on the monthly streamflow allows for better management of water use because it allows for greater utilization of this resource in times when there is high water availability and imposes a more realistic restriction during critical periods. Substitution of the annual Q_7,10 for the monthly Q_7,10 significantly increases the streamflow permitted in some months, for example, from December to May. Use of the criterion of 70 % of the annual Q₉₅ involves a high risk of drought in critical months, while the criterion of 70 % of the monthly Q₉₅ minimizes this risk.     

RIVERINE TRANSPORT OF NUTRIENTS AND DETRITUS TO THE APALACHICOLA BAY ESTUARY,FLORIDA1

ABSTRACT: The Applachicola River basin in northwest Florida covers an area of 3,100 square kilometers. Fifteen percent of the area is a dense bottomland hardwood forest which is periodically flooded. The annual leaf-litter fall from the flood-plain trees is a potential source of nutrients and detritus which eventually can flow into Apalachicola Bay. Transport of such material is dependent on the periodic inundation of the flood plain. The U.S. Geological Survey Apalachicola Rim Quality Assessment measured a total organic carbon flux of 2.1 × 10⁵ metric tons during the one-year period from June 3, 1979, to June 2,1980. Fluxes of total nitrogen and phosphorus during the same year were 2.1 × lo⁴ and 1.7 × lo³ metric tons, respectively. Flood characteirstics, such as prior hydrologic conditions, extent, and timing, are important in determining the amount and forms of materials transported. The 1980 spring flood produced a fourfold discharge increase over the annual mean outflow of 800 cubic meters per second. Nutrient concentrations varied little with discharge, but the 86-day spring flood accounted for 53, 60, 48, and 56 percent of the annual flux of total organic carbon, particulate organic carbon, total nitrogen, and total phosphorus, respectively. In 1980, the flood peaks, rather than the rise or recession, accounted for maximum nutrient and detritus transport.     

SURFACE WATER RESOURCES OF ST. JOHNS RIVER,FLORIDA1

ABSTRACT: The St. Johns River basin is the largest watershed entirely within the State of Florida, and is one of the few northward flowing rivers in the United States. The river basin contains 11,431 square miles, of which 9,430 square miles are drained by the river and its tributaries. The remainder drains into the Atlantic Ocean or the Intracoastal Waterway. Its largest sub-basin is the Oklawaha River basin, which has a drainage area of 2,870 square miles. Ground elevations range from sea level to 200 feet above mean sea level in the main river basin and as high as 300 feet above mean sea level in the Oklawaha River basin. This study was designed to investigate the surface water resources of the St. Johns River and the existing consumptive uses. The analysis revealed that the river is an extremely large and valuable resource which has been under-utilized and could play a much stronger role in serving the needs of the people in the basin.     

Effect of Human Activities on Overall Trend of Sedimentation in the Lower Yellow River,China

The Yellow River has been intensively affected by human activities, particularly in the past 50 years, including soil–water conservation in the upper and middle drainage basin, flood protection in the lower reaches, and flow regulation and water diversion in the whole drainage basin. All these changes may impact sedimentation process of the lower Yellow River in different ways. Assessing these impacts comprehensively is important for more effective environmental management of the drainage basin. Based on the data of annual river flow, sediment load, and channel sedimentation in the lower Yellow River between 1950 and 1997, the purpose of this paper is to analyze the overall trend of channel sedimentation rate at a time scale of 50 years, and its formative cause. It was found in this study that erosion control measures and water diversion have counteractive impacts on sedimentation rate in the lower Yellow River. Although both annual river flow and sediment decreased, there was no change in channel sedimentation rate. A regression analysis indicated that the sedimentation in the lower Yellow River decreased with the sediment input to the lower Yellow River but increased with the river flow input. In the past 30–40 years, the basin-wide practice of erosion and sediment control measures resulted in a decline in sediment supply to the Yellow River; at the same time, the human development of water resources that required river flow regulation and water diversion caused great reduction in river flow. The former may reduce the sedimentation in the lower Yellow River, but the reduction of river flow increased the sedimentation. When their effects counterbalanced each other, the overall trend of channel sedimentation in the lower Yellow River remained unchanged. This fact may help us to better understand the positive and negative effects of human activities in the Yellow River basin and to pay more attention to the negative effect of the development of water resources. The results of this study demonstrate that, if the overuse of river water cannot be controlled, the reduction of channel sedimentation in the lower Yellow River cannot be realized through the practice of erosion and sediment control measures.     

APPLICATION OF A LOW-FLOW ASSESSMENT MODEL FOR THE MONONGAHELA RIVER BASIN1

ABSTRACT: The application of a low-flow assessment model is illustrated for the Monogahela River Basin. The model simulates the impact of reservoir operating rules and consumptive use limitation policies on low-flow frequency at downstream locations in the basin. Policies are evaluated using an observed flow sequence and synthetic flow inputs. The paper reviews the historical development of flow management on the Monogahela to provide background for the current study.     

Stationarity of Streamflow Records and Their Influence on Bankfull Regional Curves1

Haucke, Jessica and Katherine A. Clancy, 2011. Stationarity of Streamflow Records and Their Influence on Bankfull Regional Curves. Journal of the American Water Resources Association (JAWRA) 47(6):1338–1347. DOI: 10.1111/j.1752‐1688.2011.00590.x Abstract: Bankfull regional curves, which are curves that establish relationships among channel morphology, discharge, drainage area, are used extensively for stream restoration. These curves are developed upon the assumption that streamflows maintain stationarity over the entire record. We examined this assumption in the Driftless Area of southwestern Wisconsin where agricultural soil retention practices have changed, and precipitation has increased since the 1970s. We developed a bankfull regional curve for this area using field surveys of bankfull channel performed during 2008‐2009 and annual series of peak streamflows for 10 rivers with streamflow records ranging from the 1930s to 2009. We found bankfull flows to correlate to a 1.1 return period. To evaluate gage data statistics, we used the sign test to compare our channel morphology to historic 1.5 return period discharge (Q_1.5) for five time periods: 1959‐1972, 1973‐1992, 1993‐2008, 1999‐2008, and the 1959‐2008 period of record. Analysis of the historic gage data indicated that there has been a more than 30% decline in Q_1.5 since 1959. Our research suggests that land conservation practices may have a larger impact on gaging station stationarity than annual precipitation changes do. Additionally, historic peak flow data from gages, which have records that span land conservation changes, may need to be truncated to represent current flow regimes.     

River channel network design for drought and flood control: A case study of Xiaoqinghe River basin, Jinan City, China

Vulnerability of river channels to urbanization has been lessened by the extensive construction of artificial water control improvements. The challenge, however, is that traditional engineering practices on isolated parts of a river may disturb the hydrologic continuity and interrupt the natural state of ecosystems. Taking the Xiaoqinghe River basin as a whole, we developed a river channel network design to mitigate river risks while sustaining the river in a state as natural as possible. The river channel risk from drought during low-flow periods and flood during high-flow periods as well as the potential for water diversion were articulated in detail. On the basis of the above investigation, a network with “nodes” and “edges” could be designed to relieve drought hazard and flood risk respectively. Subsequently, the shortest path algorithm in the graph theory was applied to optimize the low-flow network by searching for the shortest path. The effectiveness assessment was then performed for the low-flow and high-flow networks, respectively. For the former, the network connectedness was evaluated by calculating the “gamma index of connectivity” and “alpha index of circuitry”; for the latter, the ratio of flood-control capacity to projected flood level was devised and calculated. Results show that the design boosted network connectivity and circuitry during the low-flow periods, indicating a more fluent flow pathway, and reduced the flood risk during the high-flow periods.     

SIMULATION OF THE EFFECTS OF URBANIZATION ON BASIN STREAMFLOW1

ABSTRACT: The hydrologic modeling of streamflow in the Waterford River Basin has been conducted as part of comprehensive investigations of the effects of urbanization on water resources in the basin. Using a detailed input data base, continuous simulation of streamflow in the study area has been done by means of the HSPF model, which has been calibrated for the existing conditions and then applied to several future land use scenarios. The basin climate and geology contribute to high conversion of precipitation into streamflow under the existing conditions. Consequently, future urban development in the study basin should not increase the annual streamflow, but would contribute to increases in peak flows and the incidence of flooding because of the increased speed of runoff. If the impervious area in the basin is doubled, the peak flows may increase by about 20 percent.     

RELATION OF NITRATE CONCENTRATIONS TO BASEFLOW IN THE RACCOON RIVER,IOWA1

ABSTRACT: Excessive nitrate‐nitrogen (nitrate) export from the Raccoon River in west central Iowa is an environmental concern to downstream receptors. The 1972 to 2000 record of daily streamflow and the results from 981 nitrate measurements were examined to describe the relation of nitrate to streamflow in the Raccoon River. No long term trends in streamflow and nitrate concentrations were noted in the 28‐year record. Strong seasonal patterns were evident in nitrate concentrations, with higher concentrations occurring in spring and fall. Nitrate concentrations were linearly related to streamflow at daily, monthly, seasonal, and annual time scales. At all time scales evaluated, the relation was improved when baseflow was used as the discharge variable instead of total streamflow. Nitrate concentrations were found to be highly stratified according to flow, but there was little relation of nitrate to streamflow within each flow range. Simple linear regression models developed to predict monthly mean nitrate concentrations explained as much as 76 percent of the variability in the monthly nitrate concentration data for 2001. Extrapolation of current nitrate baseflow relations to historical conditions in the Raccoon River revealed that increasing baseflow over the 20th century could account for a measurable increase in nitrate concentrations.     

BASE FLOW RECESSION RATES,LOW FLOWS,AND HYDROLOGIC FEATURES OF SMALL WATERSHEDS IN PENNSYLVANIA,USA1

This paper examines the relationships between measurable watershed hydrologic features, base flow recession rates, and the Q_7,10 low flow statistic (the annual minimum seven‐day average streamflow occurring once every 10 years on average). Base flow recession constants were determined by analyzing hydrograph recession data from 24 small (>130 km²), unregulated watersheds across five major physiographic provinces of Pennsylvania, providing a highly variable dataset. Geomorphic, hydrogeologic, and land use parameters were determined for each watershed. The base flow recession constant was found to be most strongly correlated to drainage density, geologic index, and ruggedness number (watershed slope); however, these three parameters are intercorrelated. Multiple regression models were developed for predicting the recession rate, and it was found that only two parameters, drainage density and hydrologic soil group, were required to obtain good estimates of the recession constant. Equations were also developed to relate the recession rates to Q_7,10 per unit area, and to the Q_7,10/Q₅₀ ratio. Using these equations, estimates of base flow recession rates, Q_7,10, and streamflow reduction under drought conditions can be made for small, ungaged basins across a wide range of physiography.     

Decoupling Streamflow Responses to Climate Variability and Land Use/Cover Changes in a Watershed in Northern China

Restored annual streamflow (Q_r) and measured daily streamflow of the Chaohe watershed located in northern China and associated long‐term climate and land use/cover data were used to explore the effects of land use/cover change and climate variability on the streamflow during 1961‐2009. There were no significant changes in annual precipitation (P) and potential evapotranspiration, whereas Q_r decreased significantly by 0.81 mm/yr (p < 0.001) over the study period with a change point in 1999. We used 1961‐1998 as the baseline period (BP) and 1999‐2009 the change period (CP). The mean Q_r during the CP decreased by 39.4 mm compared with that in the BP. From 1979 to 2009, the grassland area declined by 69.6%, and the forest and shrublands increased by 105.4 and 73.1%, respectively. The land use/cover change and climate variability contributed for 58.4 and 41.6% reduction in mean annual Q_r, respectively. Compared with the BP, median and high flows in the CP decreased by 38.8 and up to 75.5%, respectively. The study concludes that large‐scale ecological restoration and watershed management in northern China has greatly decreased water yield and reduced high flows due to the improved land cover by afforestation leading to higher water loss through evapotranspiration. At a large watershed scale, land use/cover change could play as much of an important role as climate variability on water resources.     

THE EFFECTS OF CLIMATE CHANGE AND IRRIGATION ON CRITERION LOW STREAMFLOWS USED FOR DETERMINING TOTAL MAXIMUM DAILY LOADS1

ABSTRACT: This paper addresses the possible impacts of global climate change on low streamflows in the Midwest, both directly, through lower precipitation, and indirectly, by rendering irrigation profitable in areas where it has found little application in the past. In the analysis presented here, streamflow data are altered to represent the effect of climate change and stream-supplied irrigation, and then used to estimate new values for two low-flow criteria, the one- and seven-day-ten-year low flows (₇Q₁₀ and ₁Q₁₀) under 20 climate change and irrigation scenarios. Additionally, the frequencies of violation of these two criteria, and multiple violations in a three-year period, are determined. Results show that the potential impact of the assumed climate change scenarios on low flow standards is substantial. A 25 percent decrease in mean precipitation results in a 63 percent reduction in design flow, even in the absence of irrigation. With irrigation, the reduction can be as much as 100 percent. The frequency of single violations of low flow criteria is found to increase several fold with irrigation. The frequency of multiple violations of low flow criteria in a three-year period is sensitive to climate change, increasing from around 20 percent to nearly 100 percent as the climate change becomes more severe.     

Snowmelt Runoff and Water Yield Along Elevation and Temperature Gradients in California’s Southern Sierra Nevada1

Hunsaker, Carolyn T., Thomas W. Whitaker, and Roger C. Bales, 2012. Snowmelt Runoff and Water Yield Along Elevation and Temperature Gradients in California’s Southern Sierra Nevada. Journal of the American Water Resources Association (JAWRA) 48(4): 667‐678. DOI: 10.1111/j.1752‐1688.2012.00641.x Abstract: Differences in hydrologic response across the rain‐snow transition in the southern Sierra Nevada were studied in eight headwater catchments – the Kings River Experimental Watersheds – using continuous precipitation, snowpack, and streamflow measurements. The annual runoff ratio (discharge divided by precipitation) increased about 0.1 per 300 m of mean catchment elevation over the range 1,800‐2,400 m. Higher‐elevation catchments have lower vegetation density, shallow soils with rapid permeability, and a shorter growing season when compared with those at lower elevations. Average annual temperatures ranged from 6.8°C at 2,400 m to 8.6 at 1,950 m elevation, with annual precipitation being 75‐95% snow at the highest elevations vs. 20‐50% at the lowest. Peak discharge lagged peak snow accumulation on the order of 60 days at the higher elevations and 20 to 30 days at the lower elevations. Snowmelt dominated the daily streamflow cycle over a period of about 30 days in higher elevation catchments, followed by a 15‐day transition to evapotranspiration dominating the daily streamflow cycle. Discharge from lower elevation catchments was rainfall dominated in spring, with the transition to evapotranspiration dominance being less distinct. Climate warming that results in a longer growing season and a shift from snow to rain would result in earlier runoff and a lower runoff ratio.     

REGIONALIZATION OF LOW-FLOW FREQUENCY ESTIMATES: AN ALABAMA CASE STUI)Y1

ABSTRACT: Low-flow estimates, as determined by probabilistic modeling of observed data sequences, are commonly used to describe certain streamflow characteristics. Unfortunately, however, reliable low-flow estimates can be difficult to come by, particularly for gaging sites with short record lengths. The shortness of records leads to uncertainties not only in the selection of a distribution for modeling purposes but also in the estimates of the parameters of a chosen model. In flood frequency analysis, the common approach to mitigation of some of these problems is through the regionalization of frequency behavior. The same general approach is applied here to the case of low-flow estimation, with the general intent of not only improving low-flow estimates but also illustrating the gains that might be attained in so doing. Data used for this study is that which has been systematically observed at 128 streamflow gaging sites across the State of Alabama. Our conclusions are that the log Pearson Type 3 distribution is a suitable candidate for modeling of Alabama low-flows, and that the shape parameter of that distribution can be estimated on a regional basis. Low-flow estimates based on the regional estimator are compared with estimates based on the use of only at-site estimation techniques.     

EFFECTS OF DIVERSIONS ON THE NORTH AMERICAN GREAT LAKES1

ABSTRACT: Water level fluctuations of the Great Lakes often have created regional controversies among the states and Canadian provinces that share this vast resource. Even though the 100-year range of their water levels is only four to five feet, episodes of high and low Great Lakes water levels have been a recurring problem throughout the twentieth century. The possibility of increased diversion and consumptive use has exacerbated the existing conflicts over how to manage this water resource. A research project evaluated the effects of interbasin diversion on the Great Lakes system and on the industries that depend on the maintenance of historical water levels, namely hydropower and commercial navigation. The simulation approach employed in this research and some of the important findings are presented. The approach is similar to that used in recent government studies of Great Lakes water level regulation. Several significant modifications were made specifically addressing the diversion issue. Aggregate annual impacts to hydropower and shipping resulting from a diversion of 10,000 cubic feet per second were found to vary from 60 to 100 million dollars. Increases in impacts as a function of diversion rate are nonlinear for the navigation industry.     

ANALYSIS OF FIRM WATER SUPPLY UNDER COMPLEX INSTITUTIONAL CONSTRAINTS1

River basin computer simulation studies often do not properly include the complex legal and institutional factors governing water allocation. These factors include formal water rights and informal borrowing agreements among the basin water users. An attempt has been made in this study to show that such factors can be included. We also show that an optimal, integrated approach to reservoir operations in a river basin can do much to alleviate the burden of new demands placed on available water resources. The procurement of a firm water supply for a proposed coal fired power plant is analyzed as a case study. An efficient river basin simulation model is used to determine the viability of a scheme for providing an annual firm water supply to the plant, with consideration of the existing water storage and demands within the basin. Given the hydrologic sequence considered, the model results show that the proposed strategy is viable in that the required firm water supply can be realized without causing harm to decreed water users in the basin. However, integrated diversion and reservoir operations are required to assure a desirable uniform rate of delivery of reusable effluent to the power plant.