Optimal operation model of a single reservoir with drought duration explicitly concerned

In this paper, a new model for a single reservoir operation optimization is proposed. The proposed model can design the optimal operation policy of a reservoir with explicit consideration of drought duration. The authors model this problem by formulating a single-stage loss function as a function of both the reservoir release and drought duration. Thereby the expected loss per period which is calculated based on the above extended single-stage loss function is minimized in infinite time horizon on the basis of Markov decision process (MDP) theory. The reliability indices are estimated as expected loss per period for specified extended loss functions. Finally, the features of the proposed model are illustrated through numerical analysis.     

我国日照时数和总辐射的空间分布场

运用多项式回归分析和双随机样本检验,模拟日照时数和总辐射及其影响因子(可照时间、总云量和天文辐射、日照百分率)年值和1月值、7月值的三度空间分布场,取得了满意结果。这可应用在无测站地区,仅凭经纬度和海拔估算出上述气候要素值,估算的平均相对误差大多在5％以下(最好的达0.3‰)。     

长江中下游汛期降水空间型及其与太平洋海温的关系

用因子分析及方差最大原则下的正交旋转技术,计算并识别长江中下游汛期(5～9月)降水场的四个空间高载荷区及相对应的因子得分系数.它们的空间、时间变化,反映了长江中下游区域的实际降水特点.赤道东太平洋海温、区域平均海温及ENSO事件都与高载荷区的汛期降水有一定的联系,所得结果可作为汛期降水短期气候预报的参考因子.     

新疆北天山地区中强震前单台地震波参数异常特征研究

强地震的孕育过程也是孕震介质的形成过程,在强震前震源附近小地震的地震波运动学,动力学特征的变化过程,则反映了孕震介质的变化过程,为研究地震的孕育,发展和发生的过程,采用单台地震波振幅比,尾波持续时间比,尾波衰减系数这３项地震波参数作为地震学短期前兆指标,分析其震兆特征,从而达到监测孕震介质变化的目的,研究结果表明,单台地震波参数能够有效地发现地震的前兆,但地震波参数的前兆图像复杂多变,不具有统一的     

Hydrogeochemical parameters for assessment of groundwater quality in the upper Gunjanaeru River basin,Cuddapah District,Andhra Pradesh,South India

In the management of water resources, quality of water is just as important as its quantity. In order to know the quality and/or suitability of groundwater for domestic and irrigation in upper Gunjanaeru River basin, 51 water samples in post-monsoon and 46 in pre-monsoon seasons were collected and analyzed for various parameters. Geological units are alluvium, shale and quartzite. Based on the analytical results, chemical indices like percent sodium, sodium adsorption ratio, residual sodium carbonate, permeability index (PI) and chloroalkaline indices were calculated. The pre-monsoon waters have low sodium hazard as compared to post-monsoon season. Residual sodium carbonate values revealed that one sample is not suitable in both the seasons for irrigation purposes due the occurrence of alkaline white patches and low permeability of the soil. PI values of both seasons revealed that the ground waters are generally suitable for irrigation. The positive values of Chloroalkaline indices in post-monsoon (80%) and in pre-monsoon (59%) water samples indicate absence of base-exchange reaction (chloroalkaline disequilibrium), and remaining samples of negative values of the ratios indicate base-exchange reaction (chloroalkaline equilibrium). Chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for both seasons indicates that most of waters are Ca–Mg–HCO₃ type. Assessment of water samples from various methods indicated that majority of the water samples in both seasons are suitable for different purposes except at Yanadipalle (sample no. 8) that requires precautionary measures. The overall quality of groundwater in post-monsoon season in all chemical constituents is on the higher side due to dissolution of surface pollutants during the infiltration and percolation of rainwater and at few places due to agricultural and domestic activities.     

Analysis of the impact of conservation measures on stream flow regime in catchments of the Loess Plateau,China

Catchments in the Loess Plateau have been under the influence of human activities for centuries. In the last four decades, soil conservation measures have accelerated and intensified. These measures were designed to reduce soil erosion, improve agricultural productivity, and enhance environmental quality. It is important to evaluate the effects of these measures on hydrology in order to develop sustainable catchment management plans in the region. This study evaluated changes in stream flow data for four selected catchments in the Loess Plateau following large‐scale soil conservation measures. The non‐parametric Mann–Kendall test was used to identify trends in annual stream flow and the results showed significant downward trends in three of the four catchments. The Pettitt test indicated that a change point occurred in 1978 in these three catchments. Annual precipitation in all the catchments showed no significant trend during the period of record. Comparison of daily flow duration curves for two 20‐year periods (1957–1978) and (1979–2003) showed significant changes in stream flow regime. Reduction in most percentile flows varied between 20 and 45%, and the reduction in low flows was greatest. Overall, the reductions in daily flow were increasing with time, with significant changes occurring in the 1990s. However, it is not clear whether these catchments have seen the full effects of the soil conservation measures, so the results of this study might underestimate the final impact of soil conservation on stream flow regime. Copyright © 2007 John Wiley & Sons, Ltd.     

二滩水电站地震遥测台网持续时间震级的研制

利用二滩水电站地震遥测台网的速度量和位移量观测记录,收集了震级ＭＬ为０．４￣５．４的４６０次地震（Δ〈２１０ｋｍ）的振动持续时间３５００多条,制作了该台网的持续时间震级公式和便查表。在方法上,不同于通常的按一次或两次曲线拟合,而采取计算机自动分段按折线拟合的方法,以阻尼最小二乘法完成其计算;在资料上,先分台制作８个子台的持续时间震级公式,在此基础上选择仪器、台基及公式中参数相近的子台,制作了适用于     

长江三峡坝区汛期降水的气候背景分析及其与北太平洋海温的关系

对长江坝区汛期降水的气候背景进行了分析后指出：坝区汛期降水异常与ＥＡＡ相关链,特别是东亚这一段遥相关型有明显联系,进而探讨了它与前期北太平洋海水温度的关系。     

黔西南日照时数对烟叶品质的影响分析

黔西南烟叶品质的好坏与气象条件密切相关,特别是日照条件对烟叶质量的影响较大,通过对1995～2006年烟叶的商品等级与日照时数的关系统计分析,探讨日照时数对黔西南烤烟质量的影响。