HYDRO-POWER SYSTEM SIMULATION TECHNIQUE1

ABSTRACT. The non-power requirements of a large hydro-power system of multiple-purpose projects often conflict with the best power peaking operation. In order to schedule an optimum multiple-purpose operation, advanced procedures that necessitate the use of computers are required. Special techniques are used in a computer program developed in the Reservoir Control Center, North Pacific Division of the Corps of Engineers that provide the ability to define operating constraints in order of priority. These techniques are easily adapted to practical reservoir regulation problems so that the program is useful in daily reservoir regulation scheduling.     

THE OPTIMAL TIME TO START THE OPERATION OF A DESALTING PLANT IN ISRAEL1

The study contains the methodology of finding the optimal time to start the operation of a desalting plant or any other non conventional source of water for agricultural use in Israel. The essence of the methodology is the moving equilibrium price and quantity of agricultural products. The market of agricultural products is represented by a single demand curve and a supply curve which is derived from the agricultural sector production function. Both the demand for and the supply of agricultural products functions are shifting over time. The marginal value product of water is the critical value that determines the optimal time of a desalting plant. The study is static in the sense that dynamic aspects per se are not dealt with-e.g. learning by doing of building and operating desalting plants. The empirical results although used for illustrative purposes can be used as reference points for other detailed and more ‘exact’ studies on water desalination.     

Scientist and policy-maker response types and times in suburban watersheds

Differences between scientist and policy-maker response types and times, or the “how” and “when” of action, constrain effective water resource management in suburbanizing watersheds. Policy-makers are often rushed to find a single policy that can be applied across an entire, homogeneous, geopolitical region, whereas scientists undertake multiyear research projects to appreciate the complex interactions occurring within heterogeneous catchments. As a result, watershed management is often practiced with science and policy out of synch. Meanwhile, development pressures in suburban watersheds create changes in the social and physical fabric and pose a moving target for science and policy. Recent and anticipated advances in the scientific understanding of urbanized catchment hydrology and pollutant transport suggest that management should become increasingly sensitive to spatial heterogeneities in watershed features, such as soil types, terrain slopes, and seasonal watertable profiles. Toward this end, policy-makers should encourage funding scientific research that characterizes the impacts of these watershed heterogeneities within a geopolitical zoning and development framework.     

The Volta Lake and Declining Rainfall and Streamflows in the Volta River Basin

This paper looks at the rainfall and streamflow patterns over two distinct time periods, i.e., 1950–1970 and 1971–1991 within the two most prominent catchments in the Volta river system – White Volta and the Oti basins. The first period (1950–1970) represents relatively vegetated catchments and low population whilst the latter (1971–1990) represents intense land use practices resulting from increased population that have severely degraded the environment. These two catchments are among the most significant contributors to the Volta lake. The Volta lake, which was formed between 1962 and 1966 in Ghana and created primarily for hydroelectric power generation, will probably be one of the greatest man-made lakes for a long time. It produces 912MW of electricity at its maximum operating capacity. Recently, there have been declines in the lake levels resulting most probably from inadequate rainfall and/or runoff from the river catchments that feed the lake. Comparisons of runoffs for the two time periods show reductions in mean streamflows of 32.5% at Saboba on the Oti and 23.1% at Nawuni on the White Volta.     

近场地震作用下框架结构的损伤机理

首先讨论了近场地面运动的特征及各种抗震规范对近场地震的设防，然后采用非线性时程分析方法，对一个10层框架结构在近场地震作用下的响应特性进行了研究。同时对该框架结构进行了Pushover分析，通过与非线性时程分析结果进行对比，说明Pushover分析方法不能正确评估结构在近场地震作用下的抗震性能。     

Water Use by Thermoelectric Power Plants in the United States1

Abstract: Thermoelectric power generation is responsible for the largest annual volume of water withdrawals in the United States although it is only a distant third after irrigation and industrial sectors in consumptive use. The substantial water withdrawals by thermoelectric power plants can have significant impacts on local surface and ground water sources, especially in arid regions. However, there are few studies of the determinants of water use in thermoelectric generation. Analysis of thermoelectric water use data in existing steam thermoelectric power plants shows that there is wide variability in unitary thermoelectric water use (in cubic decimeters per 1 kWh) within and among different types of cooling systems. Multiple‐regression models of unit thermoelectric water use were developed to identify significant determinants of unit thermoelectric water use. The high variability of unit usage rates indicates that there is a significant potential for water conservation in existing thermoelectric power plants.     

Time series in M dimensions: The one-dimensional case: Pollution in the Chicago Sanitary and Ship Canal

A nonstationary time-series model is used to examine the changes occurring at sampling stations on the Chicago Sanitary and Ship Canal. Using data from upstream sampling sites, downstream levels of dissolved oxygen, total dissolved solids, nitrates and nitrites, and ammonia are accurately predicted. The method is simple, insensitive to extreme values, and responsive to changes in the system.     

A Spatial equilibrium perspective for planning the production of electrical energy

A spatial and temporal equilibrium model of production, consumption, prices, and transmission is constructed to determine the efficient pricing and allocation of electrical energy in the United States. Regional coordination is technically feasible and economically attractive. It also maximizes environmental efficiencies. The duplication of electrical generation and transmission facilities yields a misallocation of resources.The utilities put forth specific arguments against coordinated operations. Yet in a fully integrated power system, each region would be expected to maximize the benefits of time diversity by purchasing from outside the region in lieu of the expansion of regional capacity. The Federal Energy Regulatory Commission has not yet made a serious move to encourage regional coordination and planning, but the Commission has the authority to promote such operations if it chooses to do so.The author is an economist with the Department of Energy. The views expressed are those of the author and do not necessarily represent the policies of the Department of Energy or the views of other staff members.     

STOCHASTIC MODELING OF MONTHLY AND DAILY RAINFALL SEQUENCES1

ABSTRACT: A monthly model and two daily models (I and II) are presented for the purpose of generating monthly and daily rainfall sequences in the Quae Yai river basin in Thailand. Performance of the models are evaluated by comparing the statistical parameters of the generated sequences with those from historical data. For monthly generation, Thomas-Fiering model worked satisfactorily in spite of the monthly correlations being weak, if any. Daily Model I, which assumes no persistence between daily rainfall amounts within the wet spells, could not preserve some important parameters regardless of the simplicity in model construction. Application of multi-state transition probability matrix model gave good results, although the user has to modify some parameters looking at the performance of the model for each historical record.     

人口与经济发展对植被的影响研究

植被是陆地表面主要的覆盖物，也是许多地球系统过程的重要变量。人类活动对植被的影响在区域尺度上是显著的。以重庆市为例，使用滑动平均和SG滤波对SPOT/VGT NDVI时间序列数据进行了平滑处理，结合GDP和人口栅格化数据，从时间序列和空间相关场两个方面分析了植被与人类活动因子之间的时空相关性。结果表明，从1998到2005年，植被的分布和生长状况并没有随GDP和人口的持续增加而增加。在时间序列上，植被覆盖与GDP和人口之间总体上呈显著的负相关关系；在空间上，这种相关关系表现出了较强的异质性。空间相关场表明：较强的负相关主要发生在相对发达的主城区周围，反映了快速的经济发展和城市化使得植被面积和生产力降低；然而在偏远的山区，由于经济落后同时植被覆盖较少，出现了正相关。