A continuous coupled hydrological and water resources management model

Human exploitation of water resources is widespread and its impact on hydrological fluxes is expected to increase in the future. Water use interacts in a complex manner with the hydrological system causing severe alterations of the hydrological fluxes with multifaceted feedbacks. Implementing this coupling within hydrological models is essential when dealing with the impact of human activities on water resources at all relevant scales. We contribute to the effort in developing models coupling natural and human systems with a distributed continuous model, named GEOTRANSF. The model allows to quantify, within the same framework, alterations in the natural regime and constraints and limitations to water resources availability. After presenting GEOTRANSF, an example of application to a medium-size Alpine catchment with streamflow modified by hydropower and distributed uses is discussed, followed by the analysis of the effect of suitable water uses scenarios in the same catchment.     

Major-element deficiencies inCasuarina equisetifolia

This paper discusses the land types, hydrologic characteristics and processes, and the major modification of these, in relation to mechanisms and magnitude of phosphorus losses to drains and riverine systems which discharge to the Peel-Harvey estuary. About 75% of the coastal plain part of the catchment is cleared of native vegetation and used for dryland, dairy and beef grazing. There are small areas devoted to irrigated pasture and commercial horticulture. Seventy-five percent of the soils of the catchment are sandy surfaced with a poor capacity to retain phosphorus. Though the area is flat, catchment water yields are high because of a large winter rainfall excess and low soil storage capacity. Drainage schemes have been constructed in much of the catchment to remove excess water quickly. This was required initially to allow agricultural expansion and is now important for protecting a growing infrastructure which serves the most populous region of Western Australia.     

Climate Variability Influences on Hydrological Responses of a Large Himalayan Basin

The hydrological cycle, a fundamental component of climate is likely to be altered in important ways due to climate change. In this study, the historical daily runoff has been simulated for the Chenab River basin up to Salal gauging site using a simple conceptual snowmelt model (SNOWMOD). The model has been used to study the impact of plausible hypothetical scenarios of temperature and rainfall on the melt characteristics and daily runoff of the Chenab River basin. The average value of increase in snowmelt runoff for T + 1°C, T + 2°C and T + 3°C scenarios are obtained to be 10, 28 and 43%, respectively. Whereas, the average value of increase in total streamflow runoff for T + 1°C, T + 2°C and T + 3°C are obtained to be 7, 19 and 28%, respectively. Changes in rainfall by −10 and + 10% vary the average annual snowmelt runoff over the T + 2°C scenario by −1% and + 1% only. The result shows that melt is much more sensitive to increase in temperature than to rainfall.     

基于有偏小波网络的非线性时间序列分析

针对小波网络计算过程中出现大量冗余的特点，提出一种有偏小波网络模型。该模型在网络中添加一个偏倚层，通过自适应调整参数，增加自由度，减少计算冗余，同时采用基于多分辨率的初始化框架，加快了收敛速度，提高了计算精度。仿真计算表明，有偏小波网络能够反映非线性时间序列的内在特性，得到较好的径流预报结果，是一种有效的非线性建模方法。     

Statistical Assessment of the Impact of Conservation Measures on Streamflow Responses in a Watershed of the Loess Plateau, China

The objective of this study was to examine the trends of changes in streamflow in a watershed of the Loess Plateau, where a series of soil conservation measures were implemented since the late 1950s. Both parametric and non-parametric Mann–Kendall test were used to identify the trends in hydrologic variables over the last 50 years, and it showed significant downward trends in annual runoff, surface runoff and baseflow. The Pettitt’s test was used to detect the change points of runoff, which occurred in 1973, and the whole 50-year records could be divided into contrast (from 1957 to 1973) and treated (from 1974 to 2006) periods. It was observed that the average annual runoff during treated period reduced by 60%, surface runoff and baseflow reduced by 65% and 55%, respectively in comparing with the contrast period. But the proportion of baseflow to total runoff showed a significant increasing from 0.57 to 0.63. Seasonal runoff also showed decreased trend with the highest reduction occurring in summer and lowest in winter. Annual precipitation in whole period showed no significant trend, so the changes in hydrologic variables were induced by conservation measures. Comparison of the flow duration curves for the two periods showed that reductions in high and low flows varied greatly. Results showed that conservation measures have resulted obvious changes in the hydrologic variables in a watershed of Loess Plateau.     

基于最大熵原理的水文干旱指标计算方法研究

确定水文变量的概率分布,是计算各类标准化干旱指标的关键。提出了基于最大熵原理(POME)的月径流分布构建方法,采用多阶矩作为求解最大熵的约束条件,以拉格朗日乘子法估计分布参数,计算了不同时间尺度的标准化径流干旱指数SDI,评估了汉江30个子流域历史水文干旱情势。结果表明:与Normal、Gamma、Weibull、Pearson TypeⅢ等常用概率分布相比,POME分布模型可以最大程度地利用实测水文数据中的信息,有效拟合不同时间尺度的累积月径流量,表现出良好的适用性;随着时间尺度的增大,采用不同分布拟合同一尺度的月径流量,差别逐渐减小,月径流量概率分布特征趋于正态化。成果可为推求干旱指标,研究干旱特征的统计规律,进行干旱频率分析等提供新的手段。     

The Influence of Sampling Frequency on Streamflow Chemical Loads

In this paper, monthly loads in the streamflows from a number of UK catchments were calculated using all available chemical data and two degraded data sets comprising one value per month, thus simulating the 'harmonized monitoring scheme'of the Environment Agency † . These degraded data sets represent the lowest and highest concentrations of the various chemical determinands. Two-load calculation algorithms were used; one employing continuous-flow records plus instantaneous values, and the other employing instantaneous values only. The results of these algorithms were compared for each determinand - in terms of absolute values and the range of values possible using the degraded monthly sampling intervals.     

Theoretical Development of Stage-Discharge Ratings for Subcritical Open-Channel Flows

Ratings relating stage and flow discharge have been traditionally established through measurements of discharge and concurrent stage. Inherent in this approach are several difficulties and shortcomings that have resulted in widely recognized problems in developing and applying ratings, such as looped ratings. Purely empirical methods that attempt to improve the agreement between ratings and measurements have met with limited success. This paper suggests a theoretical basis for discharge ratings that reflects the hydraulics of unsteady, nonuniform, subcritical flow. Simplification of the Saint-Venant equations for rating applications results in an approximation of the dynamics of flow that is summarized in the hydraulic performance graph, from which discharge ratings can be developed and updated theoretically. The resulting ratings apply a quasi-steady approximation of the flow, along with semiempirical correction factors developed for the site to estimate the discharge using the same information that is needed for “stage-fall-discharge ratings,” while addressing some of the shortcomings of this type of rating. Comparison of ratings developed using the resulting procedure against laboratory and field observations yields encouraging results.     

Analysis and Synthesis of Transmission Loss Hydrographs

Accounting for transmission losses properly is critical in hydrologic analyses in arid and semiarid climates. The objective of this research was to develop a model that could account for the spatial and temporal variations of transmission losses while routing the flow hydrograph through the channel reach. This model was based on Hortonian infiltration methods and hydrologic channel routing. While most transmission loss models predict flow volumes, the model developed herein uses hydrographs of individual storm events. A numerical optimization procedure was used to identify optimum parameter values for each of Horton’s parameters and the routing coefficient, which were then used in modeling transmission losses. Flow gauge data were obtained from the Walnut Gulch Experimental Watershed, which is located near Tucson, Ariz. Testing of this model indicates that it is able to account for transmission losses and predict downstreamflow with reasonable accuracy. To provide a measure of verification, the model was compared to predictions from Lane’s model, which is a commonly used method of accounting for transmission losses based on upstreamflow and downstreamflow volumes. Overall the two methods were found to agree fairly well though differing assumptions in the methods influence the results.