Event in the case of a single reservoir: the Ghèzala dam in Northern Tunisia

The paper focuses on the development of reservoir operating rules for dry and rainfall events, and their implementation in the case of the Ghézala dam located in northern Tunisia (characterized by Mediterranean climate). Rainfall events are defined in terms of depth and duration that are correlated to each other. A depth analysis per event is performed, conditioned on the event duration. The gamma distribution provides a good fit to depth per event, especially for events lasting at least 6 days. The event duration fits a geometric distribution, whereas the dry events during the rainy season fit a negative binomial distribution. The climatic cycle length is fitted to a gamma distribution. On this basis, many 50-year synthetic event series were generated. Every synthetic streamflow sequence obtained from synthetic rainfall sequences as well as the one derived from the historic rainfall events time series were optimized and optimal decisions were formulated. These decisions were assessed by means of multiple regression analysis to estimate the relation between the optimal decision to every stage (dry or rainfall event) and other system variables. Optimal rules, which have a linear form, were derived by predetermined useful storage interval and depend on storage, inflows and downstream demand at dry or rainfall event t. The range of t is 1–13 days (rainfall event) and 1–57 days (dry event). The rules were satisfactory for every predetermined useful storage interval. The simulated dam performance generated by the operation rules was compared with the deterministic optimum operation and the historical operation. Also included is the comparison of the implicit stochastic optimization-based operation policy per event during the water years 1985–2002.

Pressure‐driven,shoreline currents in a perennially ice‐covered,pro‐glacial lake in Antarctica,identified from a LiCl tracer injected into a pro‐glacial stream

The distribution of streamwater within ice‐covered lakes influences sub‐ice currents, biological activity and shoreline morphology. Perennially ice‐covered lakes in the McMurdo Dry Valleys, Antarctica, provide an excellent natural laboratory to study hydrologic–limnologic interactions under ice cover. For a 2 h period on 17 December 2012, we injected a lithium chloride tracer into Andersen Creek, a pro‐glacial stream flowing into Lake Hoare. Over 4 h, we collected 182 water samples from five stream sites and 15 ice boreholes. Geochemical data showed that interflow travelled West of the stream mouth along the shoreline and did not flow towards the lake interior. The chemistry of water from Andersen Creek was similar to the chemistry of water below shoreline ice. Additional evidence for Westward flow included the morphology of channels on the ice surface, the orientation of ripple marks in lake sediments at the stream mouth and equivalent temperatures between Andersen Creek and water below shoreline ice. Streamwater deflected to the right of the mouth of the stream, in the opposite direction predicted by the Coriolis force. Deflection of interflow was probably caused by the diurnal addition of glacial runoff and stream discharge to the Eastern edge of the lake, which created a strong pressure gradient sloping to the West. This flow directed stream momentum away from the lake interior, minimizing the impact of stream momentum on sub‐ice currents. It also transported dissolved nutrients and suspended sediments to the shoreline region instead of the lake interior, potentially affecting biological productivity and bedform development. Copyright © 2014 John Wiley & Sons, Ltd.     

Lateral soil–pipeline interaction in sand backfill: Effect of trench dimensions

Current analytical methodologies for the evaluation of soil pressures on laterally displaced pipelines, as in the case of differential (e.g. fault-induced) permanent ground movements, allow the use of sand fill material properties under the condition that the size of the trench is adequate so that the failure surface develops fully within the sand fill (i.e. “free field” response). The accuracy of this assumption is investigated in this paper by means of numerical analyses, which employ a number of advanced features, such as pipe-backfill interface elements, large strain formulation and mesh rezoning. Following verification against well-documented experimental data, the analyses investigate: (a) the shape and size of the failure mechanism, as well as, (b) the potential trench effects on soil pressures and pipeline strains in the case of a strike-slip fault rupture. It is shown that for small embedment depths soil failure extends to the ground surface, in the form of a general shear failure mechanism, while for larger depths it becomes progressively localized and surrounds the pipeline. It is also shown that, for most cases of pipeline diameter and embedment depth, common trench dimensions cannot contain the “free field” failure surface dimensions. Finally, analyses for limited trench dimensions, reveal that the ultimate soil pressure increases exponentially with decreasing trench width, leading to high bending strains in pipelines subjected to differential lateral ground displacements.     

Of sand and mud: Sedimentological criteria for identifying the turbidity maximum zone in a tidally influenced river

The thickness and lateral distribution of sand and mud beds and bedsets on channel bars from the tidally influenced Fraser River, British Columbia, Canada, are quantitatively assessed. Fifty‐six vibracores totalling ca 114 m of vertical section are used to tabulate bed thicknesses. Statistical calculations are undertaken for nine channel bars ranging from the freshwater and tidal zone, to the sustained brackish water and tidal zone. The data reveal that thickness trends can be organized into three groups that broadly correspond to time‐averaged hydrodynamic and salinity conditions in the various distributary channels. Thick sand beds (up to 30 cm) and thin mud beds (up to 5 cm) characterize the freshwater tidal zone. The tidal and freshwater to brackish‐water transition zone comprises thin sands (up to 10 cm) and thicker muds (up to 19 cm), and the sustained brackish water tidal zone consists of thin muds (up to 6 cm) with relatively thicker sands (up to 25 cm). The results suggest that the locus of mud deposition occurs in the tidal freshwater to brackish‐water zone, probably reflecting mud flocculation and deposition at the turbidity maximum. Landward of the turbidity maximum, mud deposition is linked to tidal influence (tidal backwater effect and reverse eddy currents on channel margins) as mud beds thin in the landward direction. These results support the hypothesis that mud deposition is greatest at the turbidity maximum and decreases in both the seaward and landward direction. This study also showcases that mud‐bed thicknesses are greatest towards the turbidity maximum and thin in both the landward and seaward direction. In the rock record, the apex of mud deposition probably marks the position of the palaeo‐turbidity maximum.     

Water Absorption Capcapability and Moisture Content Seasonal Changing of Salt-Crust in Lop Nur Dry Lake

正The Lop Nur dry salt lake,Xinjiang province,is charactered by typical physiognomy salt-crust,located in39.6-41.3N.latitude and 89.6-91.4E.longitude.The thickness of salt-crust is about from 20 cm to 100 cm,and     

河套地区典型干线的形成及其在对流触发中的作用

利用高空、加密地面、EC-ERA5(0.25o×0.25o)再分析和FY-2系列静止气象卫星云图(可见光星下点分辨率1.25 km,红外5 km)等资料,对黄河河套地区3次典型干线的形成及其在对流触发中的作用进行了详细分析.结果表明:(1)3次干线触发对流出现在中高纬度高空槽东移诱发蒙古气旋发展的背景下,高低空系统配置...     

利用地基GPS技术反演武汉地区大气可降水分

利用武汉地区的探空资料和GPS实测数据，对对流层干分量延迟、对流层加权平均温度进行了检验分析．结果表明，对于武汉地区而言，常用的大气干分量延迟模型(SAAS Hopfield and Black)存在着1-2cm的系统误差，这在利用GPS资料估算大气可降水分(PWV)时会引入2-3mm的误差；对流层加权平均温度与常用的Bevis公式也存在着一定的差异，但这种差异对PWV结果影响很小．为此，提出了校正对流层干分量延迟的方法，并利用实测数据对该方法进行了检验．实践证明，这种校正方法基本上可以消除常用干分量模型的系统误差。     

Void distributions in samples of Ottawa sand

The void distribution of saturated specimens of Ottawa sand is presented. The presence of water inside the sand specimen is detected using the magnetic resonance imaging (MRI) technique. The void distribution of the sample was determined from the image. The specimen was prepared in a non-metallic triaxial cell and was put insie a MRI apparatus to obtain the image. Two sample preparation methods (wet tamping and dry pluviation) were used to illustrate the uniformity of the samples in the initial state. The void distribution along the height of the sample and the three-dimensional orientational void distribution at different locations inside the sample were analysed. The results indicate that the sample generated by the dry-pluviation method is more uniform than the sample generated by the wet-tamping method. When the wet-tamping sample preparation technique is used, the dense sample is more uniform than the loose sample. The development of voids was investigated by a sample loaded inside the MRI device under drained compression condition. The void distribution along the height of the sample at different stages was observed. This work has demonstrated the feasibility of using the MRI technique to examine void distribution in granular material.     

Deriving leaf mass per area (LMA) from foliar reflectance across a variety of plant species using continuous wavelet analysis

Leaf mass per area (LMA), the ratio of leaf dry mass to leaf area, is a trait of central importance to the understanding of plant light capture and carbon gain. It can be estimated from leaf reflectance spectroscopy in the infrared region, by making use of information about the absorption features of dry matter. This study reports on the application of continuous wavelet analysis (CWA) to the estimation of LMA across a wide range of plant species. We compiled a large database of leaf reflectance spectra acquired within the framework of three independent measurement campaigns (ANGERS, LOPEX and PANAMA) and generated a simulated database using the PROSPECT leaf optical properties model. CWA was applied to the measured and simulated databases to extract wavelet features that correlate with LMA. These features were assessed in terms of predictive capability and robustness while transferring predictive models from the simulated database to the measured database. The assessment was also conducted with two existing spectral indices, namely the Normalized Dry Matter Index (NDMI) and the Normalized Difference index for LMA (ND_LMA).Five common wavelet features were determined from the two databases, which showed significant correlations with LMA (R²: 0.51–0.82, p < 0.0001). The best robustness (R² = 0.74, RMSE = 18.97 g/m² and Bias = 0.12 g/m²) was obtained using a combination of two low-scale features (1639 nm, scale 4) and (2133 nm, scale 5), the first being predominantly important. The transferability of the wavelet-based predictive model to the whole measured database was either better than or comparable to those based on spectral indices. Additionally, only the wavelet-based model showed consistent predictive capabilities among the three measured data sets. In comparison, the models based on spectral indices were sensitive to site-specific data sets. Integrating the ND_LMA spectral index and the two robust wavelet features improved the LMA prediction. One of the bands used by this spectral index, 1368 nm, was located in a strong atmospheric water absorption region and replacing it with the next available band (1340 nm) led to lower predictive accuracies. However, the two wavelet features were not affected by data quality in the atmospheric absorption regions and therefore showed potential for canopy-level investigations. The wavelet approach provides a different perspective into spectral responses to LMA variation than the traditional spectral indices and holds greater promise for implementation with airborne or spaceborne imaging spectroscopy data for mapping canopy foliar dry biomass.     

Determination of water requirements of the Gavkhuni wetland,Iran: A hydrological approach

This study compared three hydrological methods – low flow frequency analysis, flow duration curve (FDC), and concentration-discharge (C-D) modeling – to determine the water requirement of the Gavkhuni wetland located in an arid region of Iran. Due to the effects of water impounding upstream on the hydrological regime of the Gavkhuni's inflow after construction of the Zayandehrud dam, none of the methods produced satisfactory results.Consequent modification of the hydrological regime of the wetland's inflow using a scaling process allowed all the methods except low flow frequency analysis to dependably estimate the base flow for the wetland. The results of the C–D method revealed that this method can provide a minimum health condition from the water quality point of view, while the results of the FDC demonstrated that not only the inflow estimated using this method can supply minimum conditions in terms of water quality parameters, but it also covers most areas of the wetland, based on the results of hydraulic modeling.The results reveal that the hydrological methods implemented in this study can dependably estimate environmental water allocation for wetlands in arid and semi-arid regions when there is no detailed knowledge about the biological requirements of the wetlands' biota.