Interim report on surface water resources of Baker County, Florida

The principal sources of surface-water supplies inBaker County are the St. Marys River and its tributaries. However, the flow of many of the small tributaries is intermittent, and without storage they are not dependable sources of supply during sustained periods of deficient rainfall. Of the six stream-gaging stations in Baker County for which complete records are available, one has been in operation for 31 years and provides a long-term record upon which to base correlative estimates for extending the short-term records at the other stations. All available streamflow data to 1957 have been summarized in graphic or tabular form. The hydrologic balance between minimum streamflows and increased evaporation losses afforded by potential shallow reservoirs provides design criteria for determining the maximum surface area of effective reservoir that can be created at a selected site within Baker County. This information has been presented in graphic and tabular form in the report. (PDF has 37 pages.)

Hydrologic variability related to El Nino in the Pacific Northwest [abstract]

A preliminary statistical analysis was undertaken to evaluate whether the effect of El Nino events is apparent in variables related to hydrologic behavior. Annual precipitation, temperature and streamflow were used for three locations in Oregon representing coastal, Willamette Valley/Cascade and eastern Oregon regions. The mean and variance for periods of El Nino occurrence vs. those with no El Nino were computed. Numerical differences were observed but were not consistent across all stations. The coastal area showed a decrease in mean precipitation and increase in mean streamflow during El Nino events. Other stations showed a positive increase in mean for both precipitation and streamflow for El Nino events. Variance of precipitation was greater in the coastal area but smaller in other areas and vice versa for streamflow during El Nino events. Statistical analyses indicated no significant differences of means, variances or distributions using nonparametric tests for El Nino vs. non-El Nino series.

Annual stream flow variability over the western United States [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The variability of mean annual streamflow over the western United States is described and related to indices of large scale atmospheric circulation over the Pacific Ocean and western U.S. Principal component analysis reveal [sic] four statistically significant modes of streamflow variability across the region.

Initial formation of the U.S. Geological Survey hydroclimatic data network [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The U.S. Geological Survey is working to define a hydroclimatic data network. The Geological Survey collects stream discharge data at more than 7000 sites throughout the United States. Many of these stations are operated to supply information about specific activities such as flood control, irrigation projects, or hydropower generation. As a beginning, the Geological Survey will attempt to identify stations that represent natural streamflow. Several lists of stations representing "natural" streamflow have been complied in the past. While there is some overlap among these lists, a consistent compilation is preferred. The present effort is to produce one list identifying those stations having periods of record which would be suitable for mesoscale climatic analyses.

Flux and sources of nutrients in the Mississippi-Atchafalaya River Basin: Topic 3 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico.

Ths report addresses the following two questions: 1) What are the loads (flux) of nutrients transported from the Mississippi-Atchafalaya River Basin to the Gulf of Mexico, and where do they come from within the basin? 2) What is the relative importance of specific human activities, such as agriculture, point-source discharges, and atmospheric deposition in contributing to these loads? These questions were addressed by first estimating the flux of nutrients from the Mississippi-Atchafalaya River Basin and about 50 interior basins in the Mississippi River system using measured historical streamflow and water quality data. Annual nutrient inputs and outputs to each basin were estimated using data from the National Agricultural Statistics Service, National Atmospheric Deposition Program, and point-source data provided by the USEPA. Next, a nitrogen mass balance was developed using agricultural statistics, estimates of nutrient cycling in agricultural systems, and a geographic information system. Finally, multiple regression models were developed to estimate the relative contributions of the major input sources to the flux of nitrogen and phosphorus to the Gulf of Mexico.

Inferences from tree rings on low frequency variations in runoff in the interior western United States

EXTRACT (SEE PDF FOR FULL ABSTRACT): Low frequency variations in runoff, AD 1700-1964, in the interior western United States are inferred from smoothed tree-ring series averaged over north, central, and south regions. ... Relative locations of peaks and troughs in streamflow, precipitation, temperature, and tree-ring series suggest that annual precipitation and warm season evapotranspiration variations may both be important to low frequency fluctuations in tree growth and in streamflow.

The influence of seasonal precipitation and temperature variations on runoff in California and southwestern Oregon

EXTRACT (SEE PDF FOR FULL ABSTRACT): There is considerable seasonal-to-interannual variability in the runoff of major watersheds in the Sierra Nevada, Coastal, and Cascade ranges of California and southwestern Oregon. This variability is reflected in both the amount and timing of runoff. This study examines that variability using long historical streamflow records and seasonal mean temperature and precipitation. ... Precipitation is the only significant predictor for both amount and timing of runoff in the low elevation basins. As elevation increases, the models rely more and more on temperature to explain amount and timing of runoff.

A numerical simulation of cool/wet and warm/wet episodes in the western United States

Wintertime precipitation in the mountains of the western United States during a warm or cool period has a pronounced influence on streamflow. During a warm year, streamflow at intermediate elevations responds more immediately to precipitation events; during a cold year, much of the discharge is delayed until the snow melts in spring and summer. Previous efforts at studying these extremes have been hampered by a limited number and length of observational analyses. In this study, we augment this limited observational record by analyzing a simplified general circulation model.

Semiempirical down-scaling of GCM output to the local scale for temperature, precipitation, and runoff

EXTRACT (SEE PDF FOR FULL ABSTRACT): An empirically derived multiple linear regression model is used to relate a local-scale dependent variable (either temperature, precipitation, or surface runoff) measured at individual gauging stations to six large-scale independent variables (temperature, precipitation, surface runoff, height to the 500-mbar pressure surface, and the zonal and meridional gradient across this surface). ...The area investigated is the western United States. ... The calibration data set is from 1948 through 1988 and includes data from 268 joint temperature and precipitation stations, 152 streamflow stations (which are converted to runoff data), and 24 gridded 500-mbar pressure height nodes.

Climatological aspects of the large-scale hydrologic cycle in the United States

We describe a 2.5-degree gridpoint atmospheric hydrology/climatology of precipitable water, precipitation, atmospheric moisture convergence, and a residual evaporation or evapotranspiration for the coterminous United States. We also describe a large-scale surface hydrology/climatology of a residual soil moisture, streamflow divergence, or runoff, as well as precipitation and evaporation. Annual and seasonal means and interrelationships among various components of the hydrologic cycles are discussed.

Reconstructing 20th century flood patterns in Havasu Creek, Arizona, using historical and dendrochronologic data [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Havasu Creek is the second largest tributary of the Colorado River in Grant Canyon. Perennial streamflow in the creek seldom exceeds 2 cubic meters per second, but it supports an important riparian habitat as well as unique travertine pools and waterfalls that attract over 20,000 tourists annually. Havasu Canyon is also home to over 400 members of the Havasu Tribe. Despite a long history of habitation and recreation in Havasu Canyon, streamflow records for Havasu Creek are extremely limited, making flood prediction difficult.

黄河中游地区年径流对土地利用变化时空响应分析

以黄河中游河龙区间为研究区,以水土流失综合治理及生态环境建设导致的土地利用/覆被变化为背景,采用非参数统计法,基于区内38个水文站20世纪50年代至2000年水文数据,分析流域年径流对土地利用/覆被变化响应的时空变异特征,估算影响因素贡献率。结果表明:其中29条流域年径流量呈显著减少趋势,变率为0.17~2.61 mm/a;28条流域年径流量具有显著跃变时间,无定河流域各水文站跃变时间多在1970—1973年间,其余则多为1978—1985年,最晚为1994年;在5%、50%和95%的发生频率上,跃变前后时段年径流量减少幅度以30%~60%普遍,最大分别为73.2%、63.5%和69.7%;河龙区间整体呈显著减少趋势,变率为0.79 mm/a,跃变时间发生在1979年,3个频率上的减少幅度分别为46.5%、42.4%和24.1%。估算的11条流域中有9条土地利用/覆被变化等人类活动对流域径流减少影响程度超过50%。水土保持措施面积的增加,尤其淤地坝等水利水保工程措施的持续修建,对区域地表径流变化具有明显影响。

延河流域径流和输沙周期变化特征的小波分析

用延河流域甘谷驿站1953—2000年实测月径流深和输沙模数数据和1957—2000年月均面降雨数据,采用小波多尺度方法,分析延河流域主要水文要素的周期及其变化特征。结果表明:延河流域降雨、径流和输沙存在着显著的周期,且其大小非常接近,为3.0、6.5、13.0和23.0 a。降雨、径流和输沙主周期分别是3.0、23.0和23.0 a。延河流域20世纪70年代后降雨量年际分配趋于均匀。3 a对应的小尺度上,70—80年代初3个水文序列对应曲线出现紊乱现象,与该时期大规模水利水土保持措施的修建有关。80年代后,由于水利水土保持措施减水减沙效益的削弱,3条曲线重新趋于一致。13 a对应的中尺度和23 a对应的大尺度上,均出现径流和输沙曲线不同步,或者滞后于降雨曲线现象。降水是径流和输沙周期性变化的主要外动力因子,人类活动导致的流域下垫面变化则是不可忽视的另一重要原因。

Impacts of land use change and climate variations on annual inflow into Miyun Reservoir,Beijing, China

The Miyun Reservoir, the only surface water source for Beijing city, has experienced water supply decline in recent decades. Previous studies suggest that both land use change and climate contribute to the changes of water supply in this critical watershed. However, the specific causes of the decline in the Miyun Reservoir are debatable under a non-stationary climate in the past 4 decades. The central objective of this study was to quantify the separate and collective contributions of land use change and climate variability to the decreasing inflow into the Miyun Reservoir during 1961–2008. Different from previous studies on this watershed, we used a comprehensive approach to quantify the timing of changes in hydrology and associated environmental variables using the long-term historical hydrometeorology and remote-sensing-based land use records. To effectively quantify the different impacts of the climate variation and land use change on streamflow during different sub-periods, an annual water balance model (AWB), the climate elasticity model (CEM), and a rainfall–runoff model (RRM) were employed to conduct attribution analysis synthetically. We found a significant (p  <  0.01) decrease in annual streamflow, a significant positive trend in annual potential evapotranspiration (p  <  0.01), and an insignificant (p  >  0.1) negative trend in annual precipitation during 1961–2008. We identified two streamflow breakpoints, 1983 and 1999, by the sequential Mann–Kendall test and double-mass curve. Climate variability alone did not explain the decrease in inflow to the Miyun Reservoir. Reduction of water yield was closely related to increase in actual evapotranspiration due to the expansion of forestland and reduction in cropland and grassland, and was likely exacerbated by increased water consumption for domestic and industrial uses in the basin. The contribution to the observed streamflow decline from land use change fell from 64–92 % during 1984–1999 to 36–58 % during 2000–2008, whereas the contribution from climate variation climbed from 8–36 % during the 1984–1999 to 42–64 % during 2000–2008. Model uncertainty analysis further demonstrated that climate warming played a dominant role in streamflow reduction in the most recent decade (i.e., 2000s). We conclude that future climate change and variability will further challenge the water supply capacity of the Miyun Reservoir to meet water demand. A comprehensive watershed management strategy needs to consider the climate variations besides vegetation management in the study basin.

Developing an integrated hydrograph separation and lumped modelling approach to quantifying hydrological pathways in Irish river catchments

An appreciation of the quantity of streamflow derived from the main hydrological pathways involved in transporting diffuse contaminants is critical when addressing a wide range of water resource management issues. In order to assess hydrological pathway contributions to streams, it is necessary to provide feasible upper and lower bounds for flows in each pathway. An important first step in this process is to provide reliable estimates of the slower responding groundwater pathways and subsequently the quicker overland and interflow pathways. This paper investigates the effectiveness of a multi-faceted approach applying different hydrograph separation techniques, supplemented by lumped hydrological modelling, for calculating the Baseflow Index (BFI), for the development of an integrated approach to hydrograph separation. A semi-distributed, lumped and deterministic rainfall runoff model known as NAM has been applied to ten catchments (ranging from 5 to 699 km2). While this modelling approach is useful as a validation method, NAM itself is also an important tool for investigation. These separation techniques provide a large variation in BFI, a difference of 0.741 predicted for BFI in a catchment with the less reliable fixed and sliding interval methods and local minima turning point methods included. This variation is reduced to 0.167 with these methods omitted. The Boughton and Eckhardt algorithms, while quite subjective in their use, provide quick and easily implemented approaches for obtaining physically realistic hydrograph separations. It is observed that while the different separation techniques give varying BFI values for each of the catchments, a recharge coefficient approach developed in Ireland, when applied in conjunction with the Master recession Curve Tabulation method, predict estimates in agreement with those obtained using the NAM model, and these estimates are also consistent with the study catchments’ geology. These two separation methods, in conjunction with the NAM model, were selected to form an integrated approach to assessing BFI in catchments.