Showing papers on "Streamflow published in 1997"

How much water does a river need

Abstract: > * SUMMARY 1. This paper introduces a new approach for setting streamflow-based river ecosystem management targets and this method is called the 'Range of Variability Approach' (RVA). The proposed approach derives from aquatic ecology theory concerning the critical role of hydrological variability, and associated characteristics of timing, frequency, duration, and rates of change, in sustaining aquatic ecosystems. The method is intended for application on rivers wherein the conservation of native aquatic biodiversity and protection of natural ecosystem functions are primary river management objectives. 2. The RVA uses as its starting point either measured or synthesized daily streamflow values from a period during which human perturbations to the hydrological regime were negligible. This streamflow record is then characterized using thirty-two different hydrological parameters, using methods defined in Richter et al. (1996). Using the RVA, a range of variation in each of the thirty-two parameters, e.g. the values at t 1 standard deviation from the mean or the twenty-fifth to seventy-fifth percentile range, are selected as initial flow management targets. 3. The RVA targets are intended to guide the design of river management strategies (e.g. reservoir operations rules, catchment restoration) that will lead to attainment of these targets on an annual basis. The RVA will enable river managers to define and adopt readily interim management targets before conclusive, long-term ecosystem research results are available. The RVA targets and management strategies should be adaptively refined as suggested by research results and as needed to sustain native aquatic ecosystem biodiversity and integrity.

Streamflow simulation for continental-scale river basins

Abstract: A grid network version of the two-layer variable infiltration capacity (VIC-2L) macroscale hydrologic model is described VIC-2L is a hydrologically based soil- vegetation-atmosphere transfer scheme designed to represent the land surface in numerical weather prediction and climate models The grid network scheme allows streamflow to be predicted for large continental rivers Off-line (observed and estimated surface meteorological and radiative forcings) applications of the model to the Columbia River (1° latitude-longitude spatial resolution) and Delaware River (05° resolution) are described The model performed quite well in both applications, reproducing the seasonal hydrograph and annual flow volumes to within a few percent Difficulties in reproducing observed streamflow in the arid portion of the Snake River basin are attributed to groundwater-surface water interactions, which are not modeled by VIC-2L

Response characteristics of DOC flushing in an alpine catchment

Abstract: The spatial distribution of source areas and associated residence times of water in the catchment are significant factors controlling the annual cycles of dissolved organic carbon (DOC) concentration in Deer Creek (Summit County, Colorado). During spring snowmelt (April–August 1992), stream DOC concentrations increased with the rising limb of the hydrograph, peaked before maximum discharge, then declined rapidly as melting continued. We investigated catchment sources of DOC to streamflow, measuring DOC in tension lysimeters, groundwater wells, snow and streamflow. Lysimeter data indicate that near-surface soil horizons are a primary contributor of DOC to streamflow during spring snowmelt. Concentrations of DOC in the lysimeters decrease rapidly during the melt period, supporting the hypothesis that hydrological flushing of catchment soils is the primary mechanism affecting the temporal variation of DOC in Deer Creek. Time constants of DOC flushing, characterizing the exponential decay of DOC concentration in the upper soil horizon, ranged from 10 to 30 days for the 10 lysimeter sites. Differences in the rate of flushing are influenced by topographical position, with near-stream riparian soils flushed more quickly than soils located further upslope. Variation in the amount of distribution of accumulated snow, and asynchronous melting of the snowpack across the landscape, staggered the onset of the spring flush throughout the catchment, prolonging the period of increased concentrations of DOC in the stream. Streamflow integrates the catchment-scale flushing responses, yielding a time constant associated with the recession of DOC in the stream channel (84 days) that is significantly longer than the time constants observed for particular locations in the upper soil. © 1997 John Wiley & Sons, Ltd.

Ecosystem Expansion and Contraction in Streams Desert streams vary in both space and time and fluctuate dramatically in size

Abstract: St re

Relating nutrient discharges from watersheds to land use and streamflow variability

Abstract: During a 1-year period we measured discharges of water, suspended solids, and nutrients from 27 watersheds having differing proportions of cropland in the Piedmont and Coastal Plain provinces of the Chesapeake Bay drainage. Annual flow-weighted mean concentrations of nitrate and organic N and C in stream water correlated with the relative proportions of base flow and storm flow. As the proportion of base flow increased, the concentration of nitrate increased and the concentrations of organic N and C decreased. This suggests that discharge of nitrate is promoted by groundwater flow but discharges of organic N and C are promoted by surface runoff. Concentrations of N species also increased as the proportion of cropland increased. We developed a statistical model that predicts concentrations of N species from the proportions of cropland and base flow. P concentrations did not correlate with cropland or base flow but correlated with the concentration of suspended solids, which differed among watersheds.

Performance of conceptual rainfall‐runoff models in low‐yielding ephemeral catchments

Abstract: Low-yielding catchments with ephemeral streams involve highly nonlinear relationships between rainfall and runoff, and there is much less documentation and appreciation of the ability to predict streamflow in these veiy difficult cases than in humid catchments. The predictions of three conceptual rainfall-runoff models are assessed in three low-yielding, emphemeral streams over a 10-year period. The models are a simple conceptual model, Generalized Surface inFiltration Baseflow (GSFB; eight parameters), a hybrid metric/conceptual model, Identification of Hydrographs and Components from Rainfall, Evaporation and Streamflow data (IHACRES; six parameters), and a complex conceptual model, the Large Scale Catchment Model (LASCAM; 22 parameters). The Salmon (0.82 km2), Stones (15 km2), and Canning (517 km2) catchments in Western Australia were selected for their range of sizes and low runoff yields (1.6–12.2% of rainfall). Their behavior is representative of a large part of Australia and semiarid regions, where antecedent conditions are critical determinants of streamflow response to rainfall. Such catchments provide a stern test of the capability of conceptual models. Five-year calibration and validation performances were assessed with a range of statistics. The models were run daily but performance was assessed on both a daily and monthly basis by aggregating daily model streamflows and observations up to monthly. The models performed well, particularly in the monthly case where often more than 90% of the variance of observed streamflow was explained in simulation on independent periods. However, while the simple conceptual model is adequate for monthly time periods, the daily simulation results indicate that a slightly more complex model (the hybrid model or the complex conceptual model) is required for daily predictions in these dry catchments. The model simulation results extend the following notion of Jakeman and Hornberger [1993] from humid to semiarid ephemeral catchments: that a model of about six parameters, albeit in an appropriate model structure, is sufficient to characterize the information in rainfall-discharge time series over a wide range of catchment sizes. Models of such modest complexity also predict runoff with good accuracy outside calibration periods, even in ephemeral, low-yielding catchments. The simulation results highlight the critical importance of the deep groundwater and antecedent moisture conditions on stream yields in ephemeral catchments and point to the desirability of accounting for these factors in arid-zone modeling.

Fire-Related Sedimentation Events on Alluvial Fans, Yellowstone National Park, U.S.A.

Abstract: We document initiation and flow processes, deposit facies, and geomorphic effects of forest-fire-related sedimentation on small alluvial fans in Yellowstone National Park. Brief, intense convective-storm precipitation on steep basins burned in the 1988 fires produced sedimentation events involving a variety of depositional processes on fans. Over the course of all documented events, flows on fans progressed from higher to lower sediment concentration. Events were often dominated by either debris flows or relatively sediment-poor streamflow processes; in some events, however, flows ranging a over wide spectrum of sediment concentration produced significant fan deposits. Debris flows were generated by progressive sediment bulking involving pervasive surface runoff and rill erosion on st ep upper basin slopes, followed by deep incision as flows progressed down channels. Debris-flow deposits show a marked decline in thickness and coarse gravel content downfan, often with extensive distal gravel-poor facies. We recognized a relatively minor percentage of noncohesive debris-flow and hyperconcentrated-flow facies, with sorting and stratification intermediate between muddy debris-flow and streamflow facies; these were deposited where dilute flows bulked with coarse sediment by eroding channel alluvium or earlier deposits of the event. Below incised fan channels, streamflows expanded as sheetfloods, which prograded lower fans with distally fining deposits. Basins > 3 km2 typically produced streamflow events on fans, but sediment texture and availability on slopes and in channels are primary factors determining flow processes on fans of smaller basins. Burned soil surfaces provided abundant silt and clay for debris-flow generation, but because soil surface sediment was stripped and/or compacted over time, the lack of available fines resulted in dominance of streamflow processes in later events.

Hydrograph separations in an arctic watershed using mixing model and graphical techniques

Abstract: Storm hydrographs in the Upper Kuparuk River basin (142 km2) in northern Alaska were separated into source components using a mixing model and by recession analysis. In non-Arctic regions, storm flow is commonly dominated by old water, that is, water that existed in the basin before the storm. We suspected that this may not be true in Arctic regions where permafrost diminishes subsurface storage capacity. Streamflow during the snowmelt period was nearly all new water. However, all summer storms were dominated by old water. Storms in a neighboring basin were dominated by new water but much less than was the snowmelt event. Thus a large increase in old water contributions occurred following the snowmelt period. This increase continued moderately through the summer in 1994 but not in 1995. We credit the seasonal changes in old water contributions to increased subsurface storage capacity due to thawing of the active layer.

Concentration-discharge relationships in runoff from a steep, unchanneled catchment

Abstract: The observation that "old" water dominates storm runoff suggests that release of low-solute water from soils rather than rainwater must cause storm runoff dilution. This inference is supported by sprinkling experiments in an 860-m 2 catchment in the Oregon Coast Range, in which .200 mm of both high and low ionic strength precipitation produced similar concentration-discharge trends. Rainwater chemistry was buffered as it traveled through catchment soils: the amount of sprinkling-derived water in the runoff increased during long periods of steady discharge but was not accompanied by a change in runoff solute concentrations. Stored water plays a role in runoff dilution as well. Nearly all runoff from the catchment passes through underlying weathered bedrock rather than perching and discharging only through soil. Bedrock water composition appears to vary through storm events, as the average contact time of water with rock declines with increasing discharge, a behavior at odds with the concept of stable end-members.

The quest for more powerful validation of conceptual catchment models

Abstract: The power of a validation strategy (that is, its ability to discriminate between good and bad model hypotheses) depends on what kind of data are available and how the data are used to challenge the hypothesis. Several validation strategies are examined from the perspective of power and practical applicability. It is argued that validation using multiresponse data in a catchment experiencing a shift in hydrologie regime due to disturbance or extreme climatic inputs is a considerably more powerful strategy than traditional split-sample testing using streamflow data alone in undisturbed catchments. A case study testing two model hypotheses is presented using paired catchments for which multiple-response data in the form of streamflow, stream chloride, and groundwater levels were available. The first catchment, Salmon, was maintained as an established forest, while the second, Wights, was clear-felled and converted to pasture about 3 years after monitoring started. The hypotheses consider the same lumped hydrosalinity model with the first (H1) excluding a groundwater discharge zone and the second (H2) including it. It was found that even with three concurrent responses from the undisturbed Salmon catchment, H1 could not be rejected, leaving an important part of the model conceptualization unidentified. Moreover, a streamflow split-sample test for the disturbed Wights catchment failed to conclusively reject H1; parameters could be found which accurately tracked the streamflow changes following forest clearing yet produced erroneous simulations of responses such as stream chloride and groundwater storage. It was only when H1 was subjected to the scrutiny of three catchment responses from the disturbed Wights catchment that it could be rejected. This highlights the importance of challenging model hypotheses under the most demanding of tests, which, in this study, coincided with multiple-response validation in a disturbed catchment.

Estimating Ground-Water Recharge from Streamflow Hydrographs for a Small Mountain Watershed in a Temperate Humid Climate, New Hampshire, USA

Abstract: Hydrographs of stream discharge were analyzed to determine ground-water recharge for two small basins draining into Mirror Lake, New Hampshire. Two methods of hydrograph analysis developed for determining ground-water recharge were evaluated, the instantaneous recharge method and the constant recharge method. For the instantaneous recharge method, recharge is assumed to be instantaneous and uniform over the basin. For the constant recharge method, recharge is assumed to be constant and uniform over the basin for a period of weeks to months. Both methods require that a ground-water recession slope be determined. The recession slope is used directly in the calculation for the instantaneous recharge method, and it is used as a base of reference for fitting a type curve in the constant recharge method. Results of the study indicated that the estimates of ground-water recharge for both methods agree to within about 10 percent. Two approaches to the instantaneous recharge method, manual and automated, were also evaluated, and the results were statistically similar. The baseflow component of streamflow commonly is assumed to be equivalent to ground-water recharge; therefore, two methods developed for determining the baseflow component of streamflow, graphical partitioning and digital filtering, were evaluated also. Baseflow values determined by graphical partitioning of hydrographs were about 25 percent less than the ground-water recharge values. Baseflow values determined by two different approaches to the mathematical digital filtering method were generally less than baseflow determined by graphical partitioning. However, one of the approaches to digital filtering agreed reasonably well with graphical partitioning if an appropriate filter constant was used. The other approach to digital filtering resulted in baseflow values that were much less than the other baseflow values and was therefore deemed inappropriate for use on these small mountain watersheds.

Runoff from a semiarid Ponderosa pine hillslope in New Mexico

Abstract: The mechanisms by which runoff is generated in semiarid forests have been little studied. Over the past 4 years we have been investigating runoff processes in semiarid regions by continuously monitoring runoff, both surface and lateral subsurface, from an 870-m2 ponderosa pine hillslope in northern New Mexico. We have found that runoff accounts for between 3 and 11% of the annual water budget. We have also found that lateral subsurface flow is a major mechanism of runoff generation, especially following periods of above-average fall and winter precipitation. In one winter, lateral subsurface flow was equivalent to about 20% of the snowpack (about 50 mm). When antecedent soil moisture was high, lateral subsurface flow was extremely responsive to snowmelt and rainfall events and was much more dynamic than would be suggested by the low (laboratory determined) hydraulic conductivity of the soil. The rapidity with which lateral subsurface flow follows these events suggests that macropore flow is occurring. In the case of surface runoff, the major generation mechanisms are intense summer thunderstorms, prolonged frontal storms, and snowmelt over frozen soils. Surface runoff at our site took the form of infiltration-excess overland flow; this type of surface runoff has not been found to dominate at other ponderosa pine sites studied. These detailed and continuous investigations are increasing our understanding of runoff processes in semiarid forests and are thereby laying the groundwork for improved predictions, not only of runoff, but also of the concomitant transport of sediment and contaminants within and from these zones.

Regional streamflow regimes and hydroclimatology of the United States

Abstract: The dominant regions of interannual streamflow variability in the United States are defined, and their seasonality and persistence characteristics identified, using an orthogonally rotated principal components analysis (RPCA) of a climatically sensitive network of 559 stream gages for the period 1941-1988. This classification of streamflow regimes is comprehensive and unique in that separate analyses of the streamflow record, for each month of the year, are carried out to detail the month-to-month changes in the dominant streamflow patterns. Streamflow variations, or anomalies, in the Upper Mississippi, South Atlantic/Gulf, Far West, Ohio Valley, Northeast, and Eastern/Mid- Atlantic regions, as well as a pattern of opposing streamflow anomalies in the West, are observed in all seasons of the year. Anomalies in the Southern Plains and New England regions are observed in autumn, winter, and spring; those in the Rocky Mountains and Middle Mississippi regions occur in late spring and summer.

Estimation of snow and glacier-melt contribution to the chenab river, western himalaya

Abstract: The contribution of snow and glacier-melt runoff to Himalayan rivers is significant and an estimation of the amount is necessary for the development, planning, and management of water resources. In this study, the average contribution of snow and glacier-melt runoff in the annual streamflow of the Chenab River at Akhnoor was estimated using a water balance approach. For a period of 10 years (October 1982-September 1992) the total water budget of the basin was assessed; rainfall data of 25 well-distributed stations were used to compute total rainfall input to the basin, and total volume of flow was computed using discharge data at the Akhnoor gauging site. Evapotranspiration losses only from the snow-free area were taken into account, considering that evaporation from rain falling on the snow-covered area, and from the snow-covered area itself, is negligible. The snow-covered area in the basin was determined using satellite imagery. It is observed that, on average, about 70% of the area of the basin is covered with snow in March/April and this is reduced to about 24% in September/October. The average snow and glacier runoff contribution to the annual flow of the Chenab River at Akhnoor is estimated to be about 49 percent.

Calibration, Validation and Sensitivity Analysis of the MIKE-SHE Model Using the Neuenkirchen Catchment as Case Study

Abstract: Calibration and validation of the MIKE-SHE model was performed using the Neuenkirchen research catchment hydrologic characteristics and a two-year time series of stream flows at the outlet of the catchment. A reasonable match was obtained between the observed and simulated hydrograph at the catchment outlet with minor calibration effort. For the validation runs, the base flows were overestimated in the period of high rainfall intensity while the peak flows were reasonably matched. Sensitivity of the model to structural parameters such as grid size and time step, and to the functional parameters, including hydraulic resistance coefficient, surface and subsurface hydraulic properties, was investigated. The results indicated that the peak overland flow and the total overland flow were very sensitive to the flow resistance parameters and to the vertical hydraulic conductivity of the surface soil, while the peak aquifer discharge and the total aquifer discharge were sensitive to the horizontal hydraulic conductivity in the saturated zone. The model output variables considered were neither affected, to a significant extent, by the vegetation parameters nor by the specific storage coefficient.

Inferring hydrological processes in a temperate basin using isotopic and geochemical hydrograph separation: a re-evaluation

Abstract: Simultaneous monitoring of conservative and non-conservative tracers in streamflow offers a valuable means of obtaining information on the age and flow paths of water reaching the basin outlet. Previous studies of stormflow generation in a small forested basin on the Canadian Shield used isotopic (IHS) and geochemical hydrograph separations (GHS) to infer that some event water during snowmelt reaches the stream via subsurface pathways, and that surface water runoff is generated by direct precipitation on to saturated areas (DPSA) in the stream valley. These hypotheses were tested for rainfall inputs using simultaneous IHS (18O) and GHS (dissolved silica) of basin stormflow, supplemented by hydrochemical and hydrometric data from throughflow troughs installed on basin slopes. Comparison of pre-event and subsurface water hydrographs did not provide conclusive evidence for subsurface movement of event water to the stream, owing to the appreciable uncertainty associated with the hydrograph separations. However, IHSs of runoff at the soil–bedrock interface on basin slopes indicated that event water comprised 25–50% of total runoff from areas with deep soil cover, and that these contributions supplied event water flux from the basin in excess of that attributable to DPSA. The surface water component of stormflow estimated from the GHS was also largely the result of DPSA. GHS assumes that dissolved silica is rapidly and uniformly taken up by water infiltrating the soil and that water moving via surface pathways retains the low dissolved silica level of rainfall; however, neither assumption was supported by the hillslope results. Instead, results suggest that the observed depression of silica levels in basin stormflow previously attributed to dilution by DPSA was partly a function of transport of dilute event water to the channel via preferential pathways. Implications of these results for the general use of simultaneous IHS and GHS to infer hydrological processes are discussed. © 1997 by John Wiley & Sons, Ltd.

River Discharge and Wind Influence Upon Particulate Transfer at the Land Ocean Interaction: Case Study of the Rhone River Plume

Abstract: Drifters were released at the Rhone River outlet (north-western Mediterranean sea) to follow the mixing of the river plume with the marine underlying water, and to sample suspended matter during its transfer to the open Sea. Different hydrological and meteorological situations were encountered during these trackings. During the first trajectory, salinity values and river flow measurements indicate that a flood runoff occurred as an impulse with high initial velocity. The maximum transfer was completed in a day and a progressive decrease followed. Two further trajectories characterize the spreading of the river flow under steady north–north-westerly wind conditions. During the last trajectory, the role of the Rhone River flow was secondary and the buoyant river plume reacted quasi-instantaneously to a wind shift from the north to the west. Under these different environmental conditions, great variations were observed in distribution and fate of particulate matter. The decrease in salinity induced by the spreading of fresh water into the marine environment interrupted primary production and prevented its restarting whilst the riverine influence was dominant. During the spreading of runoff, a rapid concentration decrease in total suspended matter (TSM) and particulate organic carbon (POC) occurred in the vicinity of the river mouth. This implies exportation of suspended matter down through the water column. At the peak flood, the TSM concentration was high, and as much as 60% of the initial concentration of TSM was transferred down through the water column after 1 h of drifting. At the end of runoff, the TSM concentration was lower, and about 30% was exported downward. In both cases, TSM or POC concentrations remained stable after 2 h of spreading of the plume. However, the influence of wind forcing induced redispersion in the upper part of the plume of organo-mineral aggregates temporarily accumulated at the halocline.

Acid neutralization capacity measurements in surface and ground waters in the Upper River Severn, Plynlimon: from hydrograph splitting to water flow pathways

Abstract: . Acid Neutralization Capacity (ANC) data for ephemeral stream and shallow groundwater for the catchments of the upper River Severn show a highly heterogeneous system of within-catchment water flow pathways and chemical weathering on scales of less than 100m. Ephemeral streams draining permeable soils seem to be supplied mainly from shallow groundwater sources. For these streams, large systematic differences in pH and alkalinity occur due to the variability of the groundwater sources and variability in water residence times. However, the variability cannot be gauged on the basis of broad based physical information collected in the field as geology, catchment gradients and forest structure are very similar. In contrast, ephemeral streams draining impermeable soils are of more uniform chemistry as surface runoff is mainly supplied from the soil zone. Groundwater ANC varies considerably over space and time. In general, the groundwaters have higher ANCs than the ephemeral streams. This is due to increased chemical weathering from the inorganic materials in the lower soils and groundwater areas and possibly longer residence times. However, during the winter months the groundwater ANCs tend to be at their lowest due to additional event driven acidic soil water contributions and intermediate groundwater residence times. The results indicate the inappropriateness of a blanket approach to classifying stream vulnerability to acidification simply on the basis of soil sensitivity. However, the results may well indicate good news for the environmental management of acidic and acid sensitive systems. For example, they clearly indicate a large potential supply of weathering components within the groundwater zone to reduce or mitigate the acidifying effects of land use change and acidic deposition without the environmental needs for Aiming. Furthermore, the high variability of ephemeral stream runoff means that certain areas of catchments where there are specific problems associated with acidification can be identified for focused remediation work for the situation where liming is required. The case for focused field campaigns and caution against over reliance on blanket modelling approaches is suggested. The results negate the conventional generalizations within hydrology of how water moves through catchments to generate streamflow events (from Hortonian overland flow to catchment contributing areas).

Effects of slope vegetation removal on the diurnal variations of a small mountain stream

Abstract: The effect on removal of lower, mid, and upper slope vegetation on the diurnal variation in streamflow from a 46-ha catchment was observed The diurnal variation in streamflow of the small stream was measurable during the late-spring-to-late-autumn period The amplitude in streamflow variation reached a maximum in early summer and declined during autumn Observation of diurnal variations during the periods of higher flow in winter and spring showed that they may occur but were masked by much larger variations associated with storm runoff Simulation of the characteristics of the flow measurement system showed that diurnal variations can only be studied using V-notch weirs and float recorders during periods of low flow No effect of the clearing of slope vegetation on the phase of the outflow could be found However, there was evidence of a significant increase in amplitude, probably due to increased groundwater outflow from the slopes It was concluded that the diurnal variation is due to transpiration by the riparian and near-riparian vegetation only, and that the lower to mid slope vegetation plays little role in this variation Simulations suggested that increased amplitude is associated with increased flow rates, and that the amplitude is not directly affected by water use of vegetation on the catchment slopes It was concluded that the amplitude of the variation is insensitive to changes in slope hydrology and cannot be used to provide insight into deep slope processes

Kinematic Wave Modeling in Water Resources: Environmental Hydrology

Abstract: PRELIMINARIES. Hydraulic Equations for Subsurface Flow. Hydraulic Properties of Soil. SUBSURFACE FLOW. Unsaturated Flow. Subsurface Stormflow. SURFACE IRRIGATION. Flow Advance Over Porous Beds: Application to Surface Irrigation. Flow in Infiltrating Channels: Furrow Irrigation. SNOW HYDROLOGY. Movement of Water Through Snow. Glacier Flow. EROSION AND SEDIMENT YIELD. Erosion and Sediment Transport Processes. Erosion on a Plane. WATER QUALITY. Solute Transport. Solute Transport by Surface Runoff. Solute Transport in Porous Media. Sedimentation. Chromatographic Transport in Soils. STREAMLINE. Streamflow Generation. Effect of Spatial and Temporal Variability on Streamflow Hydrograph. Appendix. Index.