Understanding the Factors That Influence Headwater Stream Flows in Response to Storm Events1

Stanfield, Les W. and Don A. Jackson, 2011. Understanding the Factors That Influence Headwater Stream Flows in Response to Storm Events. Journal of the American Water Resources Association (JAWRA) 1‐22. DOI: 10.1111/j.1752‐1688.2010.00518.x Abstract: Headwater drainage features (first‐ to second‐order streams) are the capillaries of the landscape that, among other things, moderate the timing and volumes of water available to the riparian and aquatic ecosystems. How these features respond to summer rainfall is poorly understood. We studied how geology and an index of land use/land cover influenced peak flows following rainfall events in 110 headwater stream sites that were studied over a four‐month period during a drought year. Highest peak flows were observed in the most urbanized catchments and in poorly drained soils, but specific responses were variable depending on both geology and land disturbance. Redundancy analysis indicated that both surficial geology and land disturbance were important factors influencing peak flows under drought conditions. We conclude that responses of these headwater streams to individual storms during drought conditions are unpredictable from data collected using our methods, but increased peak flows were associated with increased urban and agricultural development, but mitigated by surficial geology. These findings demonstrate the challenges to accurately predict flow conditions in headwater streams during periods of extreme weather that concurrently have the greatest potential effect on biota. The combination of these challenges and importance of such events indicates the need to develop new approaches to study and manage these resources.     

Hydrologic Sensitivity to Climate and Land Use Changes in the Santiam River Basin,Oregon

Future changes in water supply are likely to vary across catchments due to a river basin's sensitivity to climate and land use changes. In the Santiam River Basin (SRB), Oregon, we examined the role elevation, intensity of water demands, and apparent intensity of groundwater interactions, as characteristics that influence sensitivity to climate and land use changes, on the future availability of water resources. In the context of water scarcity, we compared the relative impacts of changes in water supply resulting from climate and land use changes to the impacts of spatially distributed but steady water demand. Results highlight how seasonal runoff responses to climate and land use changes vary across subbasins with differences in hydrogeology, land use, and elevation. Across the entire SRB, water demand exerts the strongest influence on basin sensitivity to water scarcity, regardless of hydrogeology, with the highest demand located in the lower reaches dominated by agricultural and urban land uses. Results also indicate that our catchment with mixed rain‐snow hydrology and with mixed surface‐groundwater may be more sensitive to climate and land use changes, relative to the catchment with snowmelt‐dominated runoff and substantial groundwater interactions. Results highlight the importance of evaluating basin sensitivity to change in planning for planning water resources storage and allocation across basins in variable hydrogeologic settings.     

Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin,Nevada1

Carroll, Rosemary W.H., Greg Pohll, David McGraw, Chris Garner, Anna Knust, Doug Boyle, Tim Minor, Scott Bassett, and Karl Pohlmann, 2010. Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin, Nevada. Journal of the American Water Resources Association (JAWRA) 46(3):554-573. DOI: 10.1111/j.1752-1688.2010.00434.x Abstract: An integrated surface water and groundwater model of Mason Valley, Nevada is constructed to replicate the movement of water throughout the different components of the demand side of water resources in the Walker River system. The Mason Valley groundwater surface water model (MVGSM) couples the river/drain network with agricultural demand areas and the groundwater system using MODFLOW, MODFLOW’s streamflow routing package, as well as a surface water linking algorithm developed for the project. The MVGSM is capable of simulating complex feedback mechanisms between the groundwater and surface water system that is not dependent on linearity among the related variables. The spatial scale captures important hydrologic components while the monthly stress periods allow for seasonal evaluation. A simulation spanning an 11-year record shows the methodology is robust under diverse climatic conditions. The basin-wide modeling approach predicts a river system generally gaining during the summer irrigation period but losing during winter months and extended periods of drought. River losses to the groundwater system approach 25% of the river’s annual budget. Reducing diversions to hydrologic response units will increase river flows exiting the model domain, but also has the potential to increase losses from the river to groundwater storage.     

WATER LOSSES ALONG A REACH OF THE PECOS RIVER IN NEW MEXICO1

ABSTRACT: A reach of the Pecos River, located in eastern New Mexico, was examined to evaluate losses of river flows due to evaporation, seepage, and transpiration. An accurate assessment of the water losses along this reach is critical for determining how water rights are adjudicated for water users in the Pecos basin and interstate compact accounting. Water losses significantly impact flows through critical habitat for species protected under the Endangered Species Act. Daily losses of river flows were analyzed for the study reach that extends from immediately below the Pecos River confluence with Taiban Creek to the United States Geological Survey (USGS) gage near Acme. The analysis was completed with consideration for other processes including flood wave travel times and attenuation along with stream bank storage and returns. The analysis was completed using daily stream flow data from USGS gages located along the study reach. Empirical seasonal functions were developed to relate flow loss to the flow rate in the river. The functions were ultimately developed to provide a method for comparing the effects of different river flows on the available water supply.     

Modelling the impacts of strategic tree plantings on salt loads and flows in the Macquarie river catchment,NSW, Australia

In Australia, problems of dryland and stream salinity have recently become the focus of a National Action Plan. In many river catchments, preliminary stream salt load and salinity targets have been set to define maximum permissible export levels in 2015. Afforestation has been proposed as a strategy for meeting these targets, although several studies suggest that widespread commercial tree plantations are likely to deliver net dis-benefits. However, the impacts on stream salt loads of more localised tree plantings in high salt yielding areas have not been quantified. In this paper we use a simple empirical model to predict the effects of various strategic and non-strategic tree planting scenarios on flows and salt loads in the mid-Macquarie catchment, New South Wales. A simple salt routing model is then used to estimate the effect of these changes on salt loads at the end-of-valley monitoring site for the Macquarie catchment. Results suggest that widespread land management interventions will be required to meet the preliminary salt load targets for this catchment. On their own, small-scale, strategic tree planting in high salt export areas of the mid-Macquarie area will not have a significant impact on salt loads at the end-of-valley monitoring site. While widespread tree plantings may reduce salt loads in the longer term, they are likely to cause streamflow losses in the shorter term. Thus, stream salinities are expected to rise initially, due to the different response times of groundwater and surface water systems to land use change.     

Inputs of nutrients and fecal bacteria to freshwaters from irrigated agriculture: case studies in Australia and New Zealand

Increasing demand for global food production is leading to greater use of irrigation to supplement rainfall and enable more intensive use of land. Minimizing adverse impacts of this intensification on surface water and groundwater resources is of critical importance for the achievement of sustainable land use. In this paper we examine the linkages between irrigation runoff and resulting changes in quality of receiving surface waters and groundwaters in Australia and New Zealand. Case studies are used to illustrate impacts under different irrigation techniques (notably flood and sprinkler systems) and land uses, particularly where irrigation has led to intensification of land use. For flood irrigation, changes in surface water contaminant concentrations are directly influenced by the amount of runoff, and the intensity and kind of land use. Mitigation for flood irrigation is best achieved by optimizing irrigation efficiency. For sprinkler irrigation, leaching to groundwater is the main transport path for contaminants, notably nitrate. Mitigation measures for sprinkler irrigation should take into account irrigation efficiency and the proximity of intensive land uses to sensitive waters. Relating contaminant concentrations in receiving groundwaters to their dominant causes is often complicated by uncertainty about the subsurface flow paths and the possible pollutant sources, viz. drainage from irrigated land. This highlights the need for identification of the patterns and dynamics of surface and subsurface waters to identify such sources of contaminants and minimize their impacts on the receiving environments.     

Integrated watershed/river catchment planning and management: a comparison of selected Canadian and United Kingdom experiences

Whilst river catchments are axiomatic units to hydrological science, their use as administrative boundaries, even within the water function, is highly dependent upon socio‐political considerations. In moves to accomplish sustainable development, with its emphasis on proactive community procedures, the catchment/basin unit is, however, receiving detailed attention—notably in England/Wales and in Canada. This paper catalogues the patterns and processes of catchment planning on both sides of the Atlantic via case studies in Ontario and southern England (Thames). Conclusions are that scale, tradition (of consultation) and information about land‐use effects on river behaviour are important controls on the rates and styles of implementation.     

Climate Change and River Ecosystems: Protection and Adaptation Options

Rivers provide a special suite of goods and services valued highly by the public that are inextricably linked to their flow dynamics and the interaction of flow with the landscape. Yet most rivers are within watersheds that are stressed to some extent by human activities including development, dams, or extractive uses. Climate change will add to and magnify risks that are already present through its potential to alter rainfall, temperature, runoff patterns, and to disrupt biological communities and sever ecological linkages. We provide an overview of the predicted impacts based on published studies to date, discuss both reactive and proactive management responses, and outline six categories of management actions that will contribute substantially to the protection of valuable river assets. To be effective, management must be place-based focusing on local watershed scales that are most relevant to management scales. The first priority should be enhancing environmental monitoring of changes and river responses coupled with the development of local scenario-building exercises that take land use and water use into account. Protection of a greater number of rivers and riparian corridors is essential, as is conjunctive groundwater/surface water management. This will require collaborations among multiple partners in the respective river basins and wise land use planning to minimize additional development in watersheds with valued rivers. Ensuring environmental flows by purchasing or leasing water rights and/or altering reservoir release patterns will be needed for many rivers. Implementing restoration projects proactively can be used to protect existing resources so that expensive reactive restoration to repair damage associated with a changing climate is minimized. Special attention should be given to diversifying and replicating habitats of special importance and to monitoring populations at high risk or of special value so that management interventions can occur if the risks to habitats or species increase significantly over time.     

Increase in phosphorus losses from grassland in response to Olsen-P accumulation

The Olsen-P status of grazed grassland (Lolium perenne L.) swards in Northern Ireland was increased over a 5-yr period (March 2000 to February 2005) by applying different rates of P fertilizer (0, 10, 20, 40, or 80 kg P ha(-1) yr(-1)) to assess the relationship between soil P status and P losses in land drainage water and overland flow. Plots (0.2 ha) were hydrologically isolated and artificially drained to v-notch weirs, with flow proportional monitoring of drainage water and overland flow. Annually, the collectors for overland flow intercepted between 11 and 35% of the surplus rainfall. Single flow events accounted for up to 52% of the annual dissolved reactive phosphorus (DRP) load. The Olsen-P status of the soil influenced DRP and total phosphorus (TP) concentrations in land drainage water and overland flow. Annual TP loss was highly variable and ranged from 0.19 to 1.55 kg P ha(-1) yr(-1) for the plot receiving no P fertilizer and from 0.35 to 2.94 kg P ha(-1) yr(-1) for the plot receiving 80 kg P ha(-1) yr(-1). Despite the Olsen-P status in the soils ranging from 22 to 99 mg P kg(-1), after 5 yr of fertilizer P applications it was difficult to identify a clear Olsen-P concentration at which P losses increased. Any relationship was confounded by annual variability of hydrologic events and flows and by hydrologic differences between plots. Withholding P fertilizer for over 5 yr was not long enough to lower P losses or to have an adverse effect on herbage P concentrations.     

Revealing the Diversity of Natural Hydrologic Regimes in California with Relevance for Environmental Flows Applications

Alterations to flow regimes for water management objectives have degraded river ecosystems worldwide. These alterations are particularly profound in Mediterranean climate regions such as California with strong climatic variability and riverine species highly adapted to the resulting flooding and drought disturbances. However, defining environmental flow targets for Mediterranean rivers is complicated by extreme hydrologic variability and often intensive water management legacies. Improved understanding of the diversity of natural streamflow patterns and their spatial arrangement across Mediterranean regions is needed to support the future development of effective flow targets at appropriate scales for management applications with minimal resource and data requirements. Our study addresses this need through the development of a spatially explicit reach‐scale hydrologic classification for California. Dominant hydrologic regimes and their physio‐climatic controls are revealed, using available unimpaired and naturalized streamflow time‐series and generally publicly available geospatial datasets. This methodology identifies eight natural flow classes representing distinct flow sources, hydrologic characteristics, and catchment controls over rainfall‐runoff response. The study provides a broad‐scale hydrologic framework upon which flow‐ecology relationships could subsequently be established towards reach‐scale environmental flows applications in a complex, highly altered Mediterranean region.     

The effects of large-scale afforestation and climate change on water allocation in the Macquarie River catchment,NSW, Australia

Widespread afforestation has been proposed as one means of addressing the increasing dryland and stream salinity problem in Australia. However, modelling results presented here suggest that large-scale tree planting will substantially reduce river flows and impose costs on downstream water users if planted in areas of high runoff yield. Streamflow reductions in the Macquarie River, NSW, Australia are estimated for a number of tree planting scenarios and global warming forecasts. The modelling framework includes the Sacramento rainfall-runoff model and IQQM, a streamflow routing tool, as well as various global climate model outputs from which daily rainfall and potential evaporation data files have been generated in OzClim, a climate scenario generator. For a 10% increase in tree cover in the headwaters of the Macquarie, we estimate a 17% reduction in inflows to Burrendong Dam. The drying trend for a mid-range scenario of regional rainfall and potential evaporation caused by a global warming of 0.5 degree C may cause an additional 5% reduction in 2030. These flow reductions will decrease the frequency of bird-breeding events in Macquarie Marshes (a RAMSAR protected wetland) and reduce the security of supply to irrigation areas downstream. Inter-decadal climate variability is predicted to have a very significant influence on catchment hydrologic behaviour. A further 20% reduction in flows from the long-term historical mean is possible, should we move into an extended period of below average rainfall years, such as occurred in eastern Australia between 1890 and 1948. Because current consumptive water use is largely adapted to the wetter conditions of post 1949, a return to prolonged dry periods would cause significant environmental stress given the agricultural and domestic water developments that have been instituted.     

Effects of flooding and drought on water quality in Gulf Coastal Plain streams in Georgia

Since 1994, water-quality constituents have been measured monthly in three adjacent Coastal Plain watersheds in southwestern Georgia. During 1994, rainfall was 650 mm above annual average and the highest flows on record were observed. From November 1998 through November 2000, 19 months had below average rainfall. Lowest flows on record were observed during the summer of 2000. The watersheds are human-dominated with row-crop agriculture and managed forestlands being the major land uses. However, one watershed (Chickasawhatchee Creek) had 10 to 13% less agriculture and greater wetland area, especially along the stream. Suspended particles, dissolved organic carbon, NH4-N, and soluble reactive phosphorus concentrations were greater during wet and flood periods compared with dry and drought periods for each stream. Regional hydrologic conditions had little effect on NO3-N or dissolved inorganic carbon. Chickasawhatchee Creek had significantly lower suspended sediment and NO3-N concentrations and greater organic and inorganic carbon concentrations, reflecting greater wetland area and stronger connection to a regional aquifer system. Even though substantial human land use occurred within all watersheds, water quality was generally good and can be attributed to low stream drainage density and relatively intact floodplain forests. Low drainage density minimizes surface run-off into streams. Floodplain forests reduce nonpoint-source pollutants through biological and physical absorption. In addition to preserving water quality, floodplain forests provide important ecological functions through the export of nutrients and organic carbon to streams. Extreme low flows may be disruptive to aquatic life due to both the lack of water and to the scarcity of biologically important materials originating from floodplain forests.     

Comparative effectiveness of discharge and input control for reducing nitrate pollution

Nitrate pollution has caused serious environmental concerns, but its control is often complicated by its diffuse nature. In most cases, nitrate control has been linked to either nitrogen input or leaching. By incorporating the relationship among land use, fertilizer application, and nitrogen leaching into a linear programming model, this analysis investigates the comparative effectiveness between input and leaching control. The empirical results from a groundwater catchment in eastern England suggest that leaching control can be more cost-effective in nitrate reduction than fertilizer input control. The implications for control of nitrate leaching through incentives systems are discussed.     

Adjusting irrigation abstraction to minimise the impact on stream flow in the East of Scotland

Abstractions of surface and groundwater for irrigation in Scotland are currently subject to control in only two small catchments. Under the terms of the EU Water Framework Directive, it will be necessary to introduce new legislation to control abstractions elsewhere. To help in the development of appropriate policy for Scotland a study has been carried out to examine the significance of irrigation and the effectiveness of different types of control strategies in terms of the economics of potato cropping and stream hydrology in Scotland. This paper presents the findings of the hydrological study and highlights some of the spatial and temporal issues that need to be considered in the selection of control mechanisms, if they are to be successful in achieving objectives for environmental improvement.The study was focussed on two catchments in the east of Scotland, the Tyne and West Peffer. The effectiveness of several different abstraction control strategies was examined to see how stream flows in the catchment would be modified by their implementation. The results of the study demonstrated that the West Peffer catchment in particular is significantly affected by irrigation abstractions. Control mechanisms based on allowable monthly abstraction volumes and flow-based abstraction bans would be of considerable help in restoring stream flows to their natural levels, but would modify the hydrological regime in slightly different ways. A spatial analysis of stream flows demonstrated that implementation of controls based on a single monitoring point may be ineffective at maintaining acceptable levels of flow throughout the catchment and that this may require a tighter control at the monitoring point.     

Evaluating stream water quality through land use analysis in two grassland catchments: impact of wetlands on stream nitrogen concentration

We evaluated the impacts of natural wetlands and various land uses on stream nitrogen concentration in two grassland-dominated catchments in eastern Hokkaido, Japan. Analyzing land use types in drainage basins, measuring denitrification potential of its soil, and water sampling in all seasons of 2003 were performed. Results showed a highly significant positive correlation between the concentration of stream NO3-N and the proportion of upland area in drainage basins in both catchments. The regression slope, which we assumed to reflect the impact on water quality, was 24% lower for the Akkeshi catchment (0.012 +/- 0.001) than for the Shibetsu catchment (0.016 +/- 0.001). In the Akkeshi catchment, there was a significant negative correlation between the proportion of wetlands in the drainage basins and stream NO3-N concentration. Stream dissolved organic nitrogen (DON) and carbon (DOC) concentrations were significantly higher in the Akkeshi catchment. Upland and urban land uses were strongly linked to increases in in-stream N concentrations in both catchments, whereas wetlands and forests tended to mitigate water quality degradation. The denitrification potential of the soils was highest in wetlands, medium in riparian forests, and lowest in grasslands; and was significant in wetlands and riparian forests in the Akkeshi catchment. The solubility of soil organic carbon (SOC) and soil moisture tended to determine the denitrification potential. These results indicate that the water environment within the catchments, which influences denitrification potential and soil organic matter content, could have caused the difference in stream water quality between the two catchments.     

The Macquarie Marshes in Arid Australia and their waterbirds: A 50-year history of decline

We investigated the relationship between total annual flow of water in the Macquarie River and the extent of flooding in the northern part of the Macquarie Marshes and trends in waterbird populations from 1983 to 1993. The amount of water in the Macquarie River measured each year within the Macquarie Marshes explained about 86% of the variation in area flooded in the northern part of this wetland. This allowed use of long-term data on flow at Oxley, a gauge within the Macquarie Marshes, as an index to flooding. Annual flows at Oxley have decreased significantly for high and medium rainfall events in the catchment, despite no trend in rainfall between 1944 and 1993. The area flooded by large floods has contracted by at least 40–50% during the last 50 years (1944–1993). Water use has progressively increased upstream in the period, depriving the Macquarie Marshes of water: 51% of all water passing Dubbo each year, a gauge 100 km upstream, reached the Macquarie Marshes in the period 1944–1953, but by 1984–1993 this had declined to 21%. Numbers of species and density of waterbirds on the northern part of the Macquarie Marshes declined between 1983 and 1993. Three other wetlands, not affected by water abstractions, showed no declines. We believe the decline was due to wetland degradation as a result of decreased flooding. We estimated more than 88,000 waterbirds in the Macquarie Marshes in October 1984, establishing the site as an important wetland site in Australia. The extent and viability of this wetland will depend on maintaining or increasing the water supply.     

The Watershed Flow and Allocation Model: An NHDPlus‐Based Watershed Modeling Approach for Multiple Scales and Conditions

The Watershed Flow and Allocation model (WaterFALL^®) provides segment‐specific, daily streamflow at both gaged and ungaged locations to generate the hydrologic foundation for a variety of water resources management applications. The model is designed to apply across the spatially explicit and enhanced National Hydrography Dataset (NHDPlus) stream and catchment network. To facilitate modeling at the NHDPlus catchment scale, we use an intermediate‐level rainfall‐runoff model rather than a complex process‐based model. The hydrologic model within WaterFALL simulates rainfall‐runoff processes for each catchment within a watershed and routes streamflow between catchments, while accounting for withdrawals, discharges, and onstream reservoirs within the network. The model is therefore distributed among each NHDPlus catchment within the larger selected watershed. Input parameters including climate, land use, soils, and water withdrawals and discharges are georeferenced to each catchment. The WaterFALL system includes a centralized database and server‐based environment for storing all model code, input parameters, and results in a single instance for all simulations allowing for rapid comparison between multiple scenarios. We demonstrate and validate WaterFALL within North Carolina at a variety of scales using observed streamflows to inform quantitative and qualitative measures, including hydrologic flow metrics relevant to the study of ecological flow management decisions.     

HYDROLOGY OF A DRAINED FORESTED POCOSIN WATERSHED1

ABSTRACT: In order to assess the effects. of silvicultural and drainage practices on water quality it is necessary to understand their impacts on hydrology. The hydrology of a 340 ha artificially drained forested watershed in eastern North Carolina was studied for a five-year period (1988–92). Effects of soils, beds and changes in vegetation on water table depth, evapotranspiration (ET) and drainage outflows were analyzed. Total annual outflows from the watershed varied from 29 percent of the rainfall during the driest year (1990) when mostly mature trees were present to as much as 53 percent during a year of normal rainfall (1992) after about a third of the trees were harvested. Annual ET from the watershed, calculated as the difference between annual rainfall and outflow, varied from 76 percent of the calculated potential ET for a dry year to as much as 99 percent for a wet year. Average estimated ET was 58 percent of rainfall for the five-year period. Flow rates per unit area were consistently higher from a smaller harvested block (Block B - 82 ha) of the watershed than from the watershed as a whole. This is likely due to time lags, as drainage water flows through the ditch-canal network in the watershed, and to timber harvesting of the smaller gaged block.     

Establishing standards and assessment criteria for ecological instream flow needs in agricultural regions of Canada

Agricultural land use can place heavy demands on regional water resources, strongly influencing the quantity and timing of water flows needed to sustain natural ecosystems. The effects of agricultural practices on streamflow conditions are multifaceted, as they also contribute to the severity of impacts arising from other stressors within the river ecosystem. Thus, river scientists need to determine the quantity of water required to sustain important aquatic ecosystem components and ecological services, to support wise apportionment of water for agricultural use. It is now apparent that arbitrarily defined minimum flows are inadequate for this task because the complex habitat requirements of the biota, which underpin the structure and function of a river ecosystem, are strongly influenced by predictable temporal variations in flow. We present an alternative framework for establishing a first-level, regional ecological instream flow needs standard based on adoption of the Indicators of Hydrologic Alteration/Range of Variability Approach as a broadly applicable hydrological assessment tool, coupling this to the Canadian Ecological Flow Index which assesses ecological responses to hydrological alteration. By explicitly incorporating a new field-based ecological assessment tool for small agricultural streams, we provide a necessary verification of altered hydrology that is broadly applicable within Canada and essential to ensure the continuous feedback between the application of flow management criteria and ecological condition.     

辽西易旱区集雨灌溉山地大棚技术

通过雨水径流的集蓄储存可解决水源问题，发展山地蔬菜大棚。结果表明：一个70m^3的水窖集水在配以渗灌技术的条件下可以满足333m^2的大棚生育期用水需求，与传统畦灌相比节水53.4%，且效益可观，达20万元／hm^2，使干旱贫瘠的山地一跃成为发展高效农业的园田，为辽西易旱区坡地高效利用开辟了一条新途径。