摘要:

The pH, electrical conductivity and runoff response of the Allt à Mharcaidh catchment is assessed for the period 1 November 1985 to 30 April 1986. Hydrographs generated by three distinct types of input are discussed; rain, snowmelt and rain-on-snow. Each produces a distinct response at the catchment outflow and the close relationship between discharge and pH emphasises the importance of hydrological factors in determining stream acidity. Interpreting the data with a view to identifying hydrological pathways, however, presents conflicting hypotheses. The data show that moorland catchments are susceptible to severe acid pulses, the most acidic being in response to snowmelt.

ISSN:0262-6667    

DOI:10.1080/02626668909491347

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper presents a procedure for a stochastic dynamic programming model conserving the performance of stochastic dynamic programming but requiring rather less computation time than the classical procedure. The approach is based upon the considerations that forecasting beyond a certain time has little effect and that this effect can be estimated approximately. It means that the forecasting horizon can be limited to less time periods than those usual in dynamic programming. An application of the method is presented for a single multipurpose reservoir. The results for autoregressive flow (lag 1) show that the forecasting horizon can be restricted to four weeks for some time periods such that real-time operating problems can be solved with a micro-computer.

ISSN:0262-6667    

DOI:10.1080/02626668909491348

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

On présente le modèle de gestion d'un barrage dont la vocation principale est la satisfaction de la demande en eau agricole, mais qui peut comporter des objectifs secondaires (fourniture d'eau potable et production d'électricité). Pour pouvoir utiliser la méthode classique de la programmation dynamique (PD) une fonction objectif particulière caractérisant l'estimation des recettes agricoles en fonction du rationnement des irrigations, est proposée. Les différentes variables aléatoires hydrologiques ou climatologiques mises en jeu dans la modélisation du problème sont traitées chacune suivant leur degré d'influence respectif. On réalise une prévision de la demande en eau d'irrigation d'une façon déterministe et on examine également l'utilisation de la PD stochastique avec prévision des probabilités d'apports hydrologiques. A partir de l'analyse des résultats de l'application de la méthode au cas du barrage de Laprade, on fait l'inventaire des différents domaines d'utilistion de cette méthode.

ISSN:0262-6667    

DOI:10.1080/02626668909491349

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The origin of the vast amount of water of the Nubian aquifer system in northeast Africa has been under controversial discussion among hydrogeologists. Does the water flow under more or less steady state conditions from intake beds in the humid Tibesti mountains or in the Ennedi mountains in Chad? Or was it recharged locally in the vicinity of the present oases during an earlier more humid climate so that present extraction actually means groundwater mining under unsteady conditions? An answer from a hydrodynamic point of view is presented using a two-dimensional horizontal finite element groundwater model simulating large-scale flow from the Chad to the Qattara depression. It includes a leakage concept for the confined northern part in order to simulate possible recharge in the vicinity of the east Saharian depressions during humid phases. According to steady state simulations, infiltration solely in the southern highlands does not suffice to maintain the presently observed water levels. Large-scale flow from the Chad highlands to the Qattara depression is insignificant. Thus the system was mainly filled by local recharge. A calibration for the 1960–1980 period was carried out on the model in order to adjust geological system parameters in the vicinity of the Egyptian depressions. An 80 years simulation for the future extraction of planned pumping centres in Egypt and Libya leads to the conclusion that there will be little interference between them in the unconfined part but a common drawdown cone in the Egyptian New Valley area. Some water extracted in Egypt will be drawn from Sudan and Libya. The existing projects in Egypt and Libya extract about 0.5 km3year−1, being the same order of magnitude as the natural groundwater discharge. The combined future projects would extract 5 km3year−1, which is about ten times the natural outflow. Thus these projects would change the natural groundwater flow system completely. A comprehensive explanation of the aquifer behaviour seems to indicate a groundwater age far beyond the apparent14C ages. Groundwater mainly flows between regions of (former) recharge and discharge. The presently extracted groundwater of the Egyptian oases was formed to a great extent during several humid phases in the unconfined part of the Nubian Aquifer in south-west Egypt. This part of the aquifer has been in a depleting process for several thousand years.

ISSN:0262-6667    

DOI:10.1080/02626668909491350

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Simulation is one method used to derive control rules. It is non-optimal. One way of circumventing the non-optimality is to employ a “control band", which may in some respects be likened to a permissible deviation from the mean (the control rule). The concept is applicable to both on- and off-stream reservoirs. The systems where the idea was developed were the Ely Ouse-Essex and later Rutland Water in the UK. The start was a “family” of simulation-derived operating rules for each reservoir. Both main frame and microcomputers were used for the Rutland Water simulation and subsequent operations. The aim was to develop an operating strategy for deployment by the controllers. Only in severe climatic abnormality would the hydrologist need to modify the programme. Warnings that problems were developing would be highlighted when actual reservoir levels were seen to fall outside the “control band". The paper gives reasons for making use of simulation and indicates some of the benefits. Possible future work to upgrade both the operation and the development of both schemes is suggested. Although simulation was used in the two cases quoted, the basic idea may also be readily adapted to forms of linear programming. Continued development of the concept of the “control band” is possible.

ISSN:0262-6667    

DOI:10.1080/02626668909491351

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The main objective of this paper is to present the results of an experimental study relating to the transport of sediment under certain conditions not typical of river sedimentation studies. The area of sediment transport lacks information on the transport down high gradient channels that are typical of streets, construction sites and agricultural land, in addition to mountain torrrents. The study of transport of non-cohesive sediment in high gradient channels includes determination of the transport capacity of shallow flows in high gradient channels with simulated bed roughness and various grain sizes. Regression analysis was performed to relate the dependent and independent variables in functional relationships and revealed good correlation.

ISSN:0262-6667    

DOI:10.1080/02626668909491352

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668909491353

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668909491354

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668909491355

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668909491356

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor