Reduction In Annual Streamflow Research Articles

Modelling the cumulative impacts of future coal mining and coal seam gas extraction on river flows: Applications of methodology

This manuscript presents examples of the modelling of the impacts of coal mining and coal seam gas extraction on streamflow in five study catchments in Australia. The manuscript includes details on data preparation and model set-up and calibration. The modelling methodology enables the prediction of cumulative impacts from multiple future coal resource developments and distributes these predictions at multiple locations in the landscape. It is framed in terms of a structured uncertainty analysis to provide information on the likelihoods and potential ranges of various impacts. Also included is a qualitative uncertainty analysis which subjectively assesses the likely impact on model results of various assumptions made during the modelling procedure. Model results suggest that, in the Australian context, maximum percentage reductions in annual streamflow are approximately commensurate with the proportion of coal mine coverage. In coal seam gas fields, reductions in annual streamflow are proportional to well density. The manuscript goes on to demonstrate how these modelling results can be used to identify a zone of potential hydrological change within a catchment. This zone delineates those parts of the landscape where water-dependent landscape classes and assets may be vulnerable to change associated with changes in the streamflow regime. A corollary of this is that any parts of the landscape outside the zone of potential hydrological change are unlikely to be affected by coal resource development.

Assessing the hydrological impacts of coal resource development: a case study from Australia

The objective of this study is to predict regional-scale cumulative impacts on water resources caused by coal resource developments in the Gloucester subregion of New South Wales (NSW), Australia. A key outcome of the assessment is identifying areas where water resources are very unlikely to be impacted (with a less than 5% chance) from those where water resources are potentially impacted (at least a 5% chance). Governments, industry and the community can then focus on areas that are potentially impacted when making regulatory, water management and planning decisions. Potential impacts were ruled out using a zone of potential hydrological change. This zone was defined based on at least a 5% chance of exceeding defined thresholds in multiple hydrological response variables including groundwater drawdown and eight streamflow metrics (only reductions in annual streamflow are reported here). The zone of potential hydrological change in the Gloucester subregion covers 250 km2 and includes 242 km of stream network. This represents 52% of the area and 70% of the stream length assessed. Groundwater drawdown exceeding 0.2 m in the near surface aquifer due to additional coal resource development is very likely (>95% chance) for an area of 20 km2 but is very unlikely (<5% chance) to exceed an area of 100 km2. Although 242 km of streams are identified as being potentially impacted, changes in streamflow are small, with a little over 5% reduction in annual flow in some streams close to the coal mines, and reductions in annual flow in the major rivers not exceeding 1 - 5%.

How streamflow has changed across Australia since the 1950s: evidence from the network of hydrologic reference stations

Abstract. Streamflow variability and trends in Australia were investigated for 222 high-quality stream gauging stations having 30 years or more continuous unregulated streamflow records. Trend analysis identified seasonal, inter-annual and decadal variability, long-term monotonic trends and step changes in streamflow. Trends were determined for annual total flow, baseflow, seasonal flows, daily maximum flow and three quantiles of daily flow. A distinct pattern of spatial and temporal variation in streamflow was evident across different hydroclimatic regions in Australia. Most of the stations in southeastern Australia spread across New South Wales and Victoria showed a significant decreasing trend in annual streamflow, while increasing trends were retained within the northern part of the continent. No strong evidence of significant trend was observed for stations in the central region of Australia and northern Queensland. The findings from step change analysis demonstrated evidence of changes in hydrologic responses consistent with observed changes in climate over the past decades. For example, in the Murray–Darling Basin, 51 out of 75 stations were identified with step changes of significant reduction in annual streamflow during the middle to late 1990s, when relatively dry years were recorded across the area. Overall, the hydrologic reference stations (HRSs) serve as critically important gauges for streamflow monitoring and changes in long-term water availability inferred from observed datasets. A wealth of freely downloadable hydrologic data is provided at the HRS web portal including annual, seasonal, monthly and daily streamflow data, as well as trend analysis products and relevant site information.

Streamflow regimes of the Yanhe River under climate and land use change, Loess Plateau, China

Soil and water conservation measures including terracing, afforestation, construction of sediment-trapping dams, and the ‘Grain for Green Program’ have been extensively implemented in the Yanhe River watershed, of the Loess Plateau, China, over the last six decades, and have resulted in large-scale land use and land cover changes. This study examined the trends and shifts in streamflow regime over the period of 1953–2010 and relates them to changes in land use and soil and water conservation and to the climatic factors of precipitation and air temperature. The non-parametric Mann–Kendall test and the Pettitt test were used to identify trends and shifts in streamflow and base flow. A method based on precipitation and potential evaporation was used to evaluate the impacts of climate variability and changes in non-climate factors changes on annual streamflow. A significant decrease (p = 0.01) in annual streamflow was observed related to a significant change point in 1996, mostly because of significant decreases in streamflow (p = 0.01) in the July to September periods in subsequent years. The annual base flow showed no significant trend from 1953 to 2010 and no change point year, mostly because there were no significant seasonal trends, except for significant decreases (p = 0.05) in the July to September periods. There was no significant trend for precipitation over the studied time period, and no change point was detected. The air temperature showed a significant increasing trend (p < 0.01), and 1986 (p < 0.01) was the change point year. The climate variability, as measured by precipitation and temperature, and non-climate factors including land use changes and soil and water conservation were estimated to have contributed almost equally to the reduction in annual streamflow. Soil and water conservation practices, including biological measures (e.g. revegetation, planting trees and grass) and engineering measures (such as fish-scale pits, horizontal trenches, and sediment-trapping dams) play an important role in reduction of the conversion of rainfall to run-off. Copyright © 2014 John Wiley & Sons, Ltd.

Adaptation of surface water supply to climate change in central Iran

Optimal reservoir operation changes and adaptation strategies for the Zayandeh-Rud River Basin's surface water supply system are examined for a changing climate during the 2015–2044 period. On average, the monthly temperature in the basin is expected to increase by 0.46–0.76 °C and annual precipitation is expected to decrease by 14–38% with climate change, resulting in a reduction of the Zayandeh-Rud's peak stream flow and the amplitude of its seasonal range. Snowfall decrease in winter months will generally lead to an 8–43% reduction in annual stream flow under climate change. A reservoir operation model is developed and optimal reservoir operation strategies are identified for adaptation of the basin's surface water supply to climate change in the face of the increasing water demand. Results indicate that the reservoir drawdown season starts 2 months earlier under climate change. Smaller storage levels and greater water releases must occur to meet the increasing water demand. The optimized water release can provide sufficient water for non-agricultural water demand, but agriculture will experience more severe water shortage under a changing climate. Having the highest vulnerability, the agricultural sector should be the main focus of regional management plans to address the current water challenge and more severe water shortages under climate change.

应用SWAT模型研究潮河流域土地利用和气候变化对径流的影响

Global warming and intensive changes in land use /cover have posted unprecedented impacts on the watershed hydrology and thus the water security at the global scale. To quantitatively analyze the impacts of land use change and climate variability on the streamflow of Chaohe Watershed located in North China,we calibrated and validated a distributed hydrological model-SWAT by using the multi-site calibration procedure. The effects of land use changes and climate variability on the stream of the watershed were then explored by using scenario analysis approach. Two indices,the p-factor,r-factor as well as efficiency of objective function,were used to assess the calibration / uncertainty performance of the SWAT model at the hydrological stations of Dage,Daiying and Xiahui within the research watershed. Results showed that p-factors in the calibration and validation periods were 0. 70 and 0. 77,0. 87 and 0. 82,0. 92 and 0. 78 respectively for the three stations. The r-factors in the calibration and validation periods were 0. 63 and 0. 90,0. 97 and 0. 79,0. 88 and 0. 92 respectively for the three stations. The objective function of efficiency of SWAT was 0.66,suggesting that the model was capable for simulating runoff responses to changes of land use and climate variability in the watershed. Compared with the baseline period( 1981—1990),land use change caused an annual streamflow reduction of 4.1 mm whereas climate change gave rise to an annual streamflow reduction of 29.7mm in the period from 1991 to 2000. For the period of 2001—2009 land use change reduced runoff by 3.0 mm,whereas climate change decreased runoff for 14.3 mm. When the land use in 1999 was set as the reference,the annual streamflow would increase by 158.2% and 4.1% for the shrub land scenario and the grassland scenario,respectively. Contrarily,the farmland scenario and the woodland scenario could induce 41. 7% and 23. 7% annual streamflow reductions,respectively. The climate variability scenario analysis indicated that a 10% increase in annual precipitation could lead to 23.9% annual streamflow increase and a 12% increase in annual mean air temperature could lead to a 6% reduction in annual streamflow. We,therefore,concluded that the annual streamflow variation was more sensitive to precipitation than to temperature in the region. It is of critical importance to develop explicitly integrated"causeeffect"land use planning and strategies for adaptive land and water management at watershed scale under the global change.

Response of streamflow to climate change and human activity in Xitiaoxi river basin in China

AbstractIn recent years, the Xitiaoxi river basin in China has experienced intensified human activity, including city expansion and increased water demand. Climate change also has influenced streamflow. Assessing the impact of climate variability and human activity on hydrological processes is important for water resources planning and management and for the sustainable development of eco‐environmental systems. The non‐parametric Mann–Kendall test was employed to detect the trends of climatic and hydrological variables. The Mann–Kendall–Sneyers test and the moving t‐test were used to locate any abrupt change of annual streamflow. A runoff model, driven by precipitation and potential evapotranspiration, was employed to assess the impact of climate change on streamflow. A significant downward trend was detected for annual streamflow from 1975 to 2009, and an abrupt change occurred in 1999, which was consistent with the change detected by the double mass curve test between streamflow and precipitation. The annual precipitation decreased slightly, but upward trends of annual mean temperature and potential evapotranspiration were significant. The annual streamflow during the period 1999–2009 decreased by 26.19% compared with the reference stage, 1975–1998. Climate change was estimated to be responsible for 42.8% of the total reduction in annual streamflow, and human activity accounted for 57.2%. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Estimating effects of plantation expansion and climate variability on streamflow for catchments in Australia

Plantation forestry is an increasingly important land use in Australia. While plantations can present significant environmental benefits such as salinity and erosion controls, their impact on streamflow needs to be recognized. This study evaluated the impacts of plantation and climate variability on streamflow from catchments in Australia. In total 15 catchments were selected based on the availability of streamflow, meteorological, and plantation information. The catchment areas range from 0.6 to 1136 km2 and represent different climatic conditions and management practices. The Mann–Kendall test was used to estimate trends in the annual streamflow, rainfall, potential evaporation, and runoff ratio. The plantation effect on streamflow was determined with the time‐trend analysis method, while the effect of climate variability was calculated using the sensitivity‐based approach. All the selected catchments showed reductions in annual streamflow and runoff ratio over the period of the records. The results indicate that plantation expansions accounted for 28% to 106% of the observed total streamflow reductions, while climate variability was responsible for 5% to 80% of the total streamflow reductions. It is evident that both plantation expansions and climate variability contributed to the observed streamflow reductions. In most of the catchments, the effect of plantation expansion on streamflow was more important than that of climate variability and is likely to have exacerbated the effect of climate variability on streamflow. Plantation expansions can reduce streamflow from both small and large catchments as this study demonstrated and the relative streamflow reduction can be linearly related to percentage plantation area in a catchment.

Assessing the impact of climate variability and human activities on streamflow from the Wuding River basin in China

AbstractLocated in the Loess Plateau of China, the Wuding River basin (30 261 km2) contributes significantly to the total sediment yield in the Yellow River. To reduce sediment yield from the catchment, large‐scale soil conservation measures have been implemented in the last four decades. These included building terraces and sediment‐trapping dams and changing land cover by planting trees and improving pastures. It is important to assess the impact of these measures on the hydrology of the catchment and to provide a scientific basis for future soil conservation planning. The non‐parametric Mann–Kendall–Sneyers rank test was employed to detect trends and changes in annual streamflow for the period of 1961 to 1997. Two methods were used to assess the impact of climate variability on mean annual streamflow. The first is based on a framework describing the sensitivity of annual streamflow to precipitation and potential evaporation, and the second relies on relationships between annual streamflow and precipitation. The two methods produced consistent results. A significant downward trend was found for annual streamflow, and an abrupt change occurred in 1972. The reduction in annual streamflow between 1972 and 1997 was 42% compared with the baseline period (1961–1971). Flood‐season streamflow showed an even greater reduction of 49%. The streamflow regime of the catchment showed a relative reduction of 31% for most percentile flows, except for low flows, which showed a 57% reduction. The soil conservation measures reduced streamflow variability, leading to more uniform streamflow. It was estimated that the soil conservation measures account for 87% of the total reduction in mean annual streamflow in the period of 1972 to 1997, and the reduction due to changes in precipitation and potential evaporation was 13%. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Changes in stream flow regime in headwater catchments of the Yellow River basin since the 1950s

AbstractThe headwater catchments of the Yellow River basin generate over 35% of the basin's total stream flow and play a vital role in meeting downstream water resources requirements. In recent years the Yellow River has experienced significant changes in its hydrological regime, including an increased number of zero‐flow days. These changes have serious implications for water security and basin management. We investigated changes in stream flow regime of four headwater catchments since the 1950s. The rank‐based non‐parametric Mann–Kendall test was used to detect trends in annual stream flow. The results showed no significant trend for the period 1956 to 2000. However, change‐point analysis showed that a significant change in annual stream flow occurred around 1990, and hence the stream‐flow data can be divided into two periods: 1956–1990 and 1991–2000. There was a considerable difference in average annual stream flow between the two periods, with a maximum reduction of 51%. Wet‐season rainfall appears to be the main factor responsible for the decreasing trend in annual stream flow. Reductions in annual stream flow were associated with decreased interannual variability in stream flow. Seasonal stream flow distribution changed from bimodal to unimodal between the two periods, with winter stream flow showing a greater reduction than other seasons. Daily stream flow regime represented by flow duration curves showed that all percentile flows were decreased in the second period. The high flow index (Q5/Q50) reduced by up to 28%, whereas the reduction in the low flow index (Q95/Q50) is more dramatic, with up to 100% reduction. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Hydrologic sensitivity of global rivers to climate change

Climate predictions from four state-of-the-art general circulation models (GCMs) were used to assess the hydrologic sensitivity to climate change of nine large, continental river basins (Amazon, Amur, Mackenzie, Mekong, Mississippi, Severnaya Dvina, Xi, Yellow, Yenisei). The four climate models (HCCPR-CM2, HCCPR-CM3, MPI-ECHAM4, and DOE-PCM3) all predicted transient climate response to changing greenhouse gas concentrations, and incorporated modern land surface parameterizations. Model-predicted monthly average precipitation and temperature changes were downscaled to the river basin level using model increments (transient minus control) to adjust for GCM bias. The variable infiltration capacity (VIC) macroscale hydrological model (MHM) was used to calculate the corresponding changes in hydrologic fluxes (especially streamflow and evapotranspiration) and moisture storages. Hydrologic model simulations were performed for decades centered on 2025 and 2045. In addition, a sensitivity study was performed in which temperature and precipitation were increased independently by 2 °C and 10%, respectively, during each of four seasons. All GCMs predict a warming for all nine basins, with the greatest warming predicted to occur during the winter months in the highest latitudes. Precipitation generally increases, but the monthly precipitation signal varies more between the models than does temperature. The largest changes in the hydrological cycle are predicted for the snow-dominated basins of mid to higher latitudes. This results in part from the greater amount of warming predicted for these regions, but more importantly, because of the important role of snow in the water balance. Because the snow pack integrates the effects of climate change over a period of months, the largest changes occur in early to mid spring when snow melt occurs. The climate change responses are somewhat different for the coldest snow dominated basins than for those with more transitional snow regimes. In the coldest basins, the response to warming is an increase of the spring streamflow peak, whereas for the transitional basins spring runoff decreases. Instead, the transitional basins have large increases in winter streamflows. The hydrological response of most tropical and mid-latitude basins to the warmer and somewhat wetter conditions predicted by the GCMs is a reduction in annual streamflow, although again, considerable disagreement exists among the different GCMs. In contrast, for the high-latitude basins increases in annual flow volume are predicted in most cases.

The response in water yield to the thinning of Pinus radiata, Pinus patula and Eucalyptus grandis plantations

The paired catchment method was used to test for the effects of thinning on the water yield in three afforested catchments in South Africa, namely, Biesievlei, Jonkershoek, 98% afforested with Pinus radiata (three thinnings); Westfalia catchment D, 100% afforested with Eucalyptus grandis (two thinnings); and Cathedral Peak CII that was 74% afforested with Pinus patula (one thinning). During and after two separate thinnings, each of which removed roughly one third of the stems in a maturing P. radiata plantation in the Biesievlei catchment, annual streamflow increased by between 10 and 71% (19–99 mm). These increases persisted for three and two years after the thinning, respectively. A final thinning in the same catchment removed only 22% of stems at an age of 28 yr. The following years (1977 and 1978) were wetter than average, and reductions in annual streamflow of 26 and 55% were recorded in these two years. At Westfalia catchment D and Cathedral Peak CII, the hydrological trends were entirely dominated by the rapidly declining streamflow caused by the developing E. grandis and P. patula plantations respectively. Any savings in water use that may have resulted from the thinning of these plantations were insufficient to affect the downward trend in annual streamflow. Thinnings may have had a minor effect of delaying or reducing the desiccation of these catchments but such effects could not be assessed due to natural variability and the limited resolution of the paired catchment method. The trends in total water yield from the catchments were generally mirrored in the dry season streamflow, and there were no strong indications that thinning effects are linked to a particular season.

POTENTIAL EFFECTS OF CLIMATE CHANGE ON FRESHWATER ECOSYSTEMS OF THE NEW ENGLAND/MID-ATLANTIC REGION

Numerous freshwater ecosystems, dense concentrations of humans along the eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the same time that climate is expected to be changing. Consequently, the effects of humans and climatic change are likely to affect freshwater ecosystems within the region interactively. The general climate, at present, is humid continental, and the region receives abundant precipitation. Climatic projections for a 2 × CO2 atmosphere, however, suggest warmer and drier conditions for much of this region. Annual temperature increases ranging from 3–5°C are projected, with the greatest increases occurring in autumn or winter. According to a water balance model, the projected increase in temperature will result in greater rates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern sections of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also projected to decrease across the region, and summer convective thunderstorms are likely to decrease in frequency but increase in intensity. The dual effects of climate change and direct anthropogenic stress will most likely alter hydrological and biogeochemical processes, and, hence, the floral and faunal communities of the region's freshwater ecosystems. For example, the projected increase in evapotranspiration and evaporation could eliminate most bog ecosystems, and increases in water temperature may increase bioaccumulation, and possibly biomagnification, of organic and inorganic contaminants. Not all change may be adverse. For example, a decrease in runoff may reduce the intensity of ongoing estuarine eutrophication, and acidification of aquatic habitats during the spring snowmelt period may be ameliorated. Recommendations for future monitoring efforts include: (1) extending and improving data on the distribution, abundance and effect of anthropogenic stressors (non-point pollution) within the region; and (2) improving scientific knowledge regarding the contemporary distribution and abundance of aquatic species. Research recommendations include: (1) establishing a research centre(s) where field studies designed to understand interactions between freshwater ecosystems and climate change can be conducted; (2) projecting the future distribution, activities and direct effects of humans within the region; (3) developing mathematical analyses, experimental designs and aquatic indicators that distinguish between climatic and anthropogenic effects on aquatic systems; (4) developing and refining projections of climate variability such that the magnitude, frequency and seasonal timing of extreme events can be forecast; and (5) describing quantitatively the flux of materials (sediments, nutrients, metals) from watersheds characterized by a mosaic of land uses. © 1997 John Wiley & Sons, Ltd.

POTENTIAL EFFECTS OF CLIMATE CHANGE ON FRESHWATER ECOSYSTEMS OF THE NEW ENGLAND/MID-ATLANTIC REGION

Numerous freshwater ecosystems, dense concentrations of humans along the eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the same time that climate is expected to be changing. Consequently, the effects of humans and climatic change are likely to affect freshwater ecosystems within the region interactively. The general climate, at present, is humid continental, and the region receives abundant precipitation. Climatic projections for a 2 x CO1 atmosphere, however, suggest warmer and drier conditions for much of this region. Annual temperature increases ranging from 3-5°C are projected, with the greatest increases occurring in autumn or winter. According to a water balance mode!, the projected increase in temperature will result in greater rates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern sections of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also projected to decrease across the region, and summer convective thunderstorms are likely to decrease in frequency but increase in intensity. The dual effects of climate change and direct anthropogenic stress will most likely alter hydrological and biogeochemica! processes, and, hence, the flora! and fauna! communities of the region’s freshwater ecosystems. For example, the projected increase in evapotranspiration and evaporation could eliminate most bog ecosystems, and increases in water temperature may increase bioaccumulation, and possibly biomagnification, of organic and inorganic contaminants. Not a!! change may be adverse. For example, a decrease in runoff may reduce the intensity of ongoing estuarine eutrophication, and acidification of aquatic habitats during the spring snowmelt period may be ameliorated. Recommendations for future monitoring efforts include: (1) extending and improving data on the distribution, abundance and effect of anthropogenic stressors (non-point pollution) within the region; and (2) improving scientific knowledge regarding the contemporary distribution and abundance of aquatic species. Research recommendations include: (1) establishing a research centre(s) where field studies designed to understand interactions between freshwater ecosystems and climate change can be conducted; (2) projecting the future distribution, activities and direct effects of humans within the region; (3) developing mathematical analyses, experimental designs and aquatic indicators that distinguish between climatic and anthropogenic effects on aquatic systems; (4) developing and refining projections of climate variability such that the magnitude, frequency and seasonal timing of extreme events can be forecast; and (5) describing quantitatively the flux of materials (sediments, nutrients, metals) from watersheds characterized by a mosaic of land uses. 0 1997 by John Wiley & Sons, Ltd.

Land-use hydrology: Shoalhaven, New South Wales

A computer model, with explicit descriptions for the major processes of the hydrologic cycle formed a basis for simulating the consequences of land-use change on streamflow in the upper Shoalhaven Valley of New South Wales. Computed streamflow for existing land use corresponded with recorded data on both the monthly and annual scales. Simulation for pasture improvement suggested that a significant reduction in annual streamflow from as high as 28% would occur in a year with average rainfall, but that this reduction would be insignificant in years of high rainfall. Afforestation of pastures with pines produced a 32% reduction in streamflow for average rainfall conditions and maintained a similar proportionate reduction in wet years.