The influence of dam and lakes on the Yangtze River streamflow: long‐range correlation and complexity analyses

Employing long‐range correlation, complexity features and clustering, this study investigated the influence of dam and lake‐river systems on the Yangtze River flow. The impact of the Gezhouba Dam and the lake systems on streamflow was evaluated by analysing daily streamflow records at the Cuntan, the Yichang and the Datong station. Results indicated no evident influence of the Gezhouba Dam on streamflow changes. Distinct differences in scaling behaviour, long‐range correlation and clustering of streamflow at the Datong station when compared with those at the Cuntan and Yichang stations undoubtedly showed the influence of water storage and the buffering effect of the lake systems between the Datong station and other two hydrological stations on streamflow in the lower Yangtze River basin. Decreased regularity, enhanced long‐range correlation and increased clustering of streamflow in the lower Yangtze River basin due to the effect of water storage of the lake systems were corroborated. Copyright © 2011 John Wiley & Sons, Ltd.     

Groundwater–surface water interactions in a lowland watershed: source contribution to stream flow

The lower coastal plain of the Southeast USA is undergoing rapid urbanisation as a result of population growth. Land use change has been shown to affect watershed hydrology by altering stream flow and, ultimately, impairing water quality and ecologic health. However, because few long‐term studies have focused on groundwater–surface water interactions in lowland watersheds, it is difficult to establish what the effect of development might be in the coastal plain region. The objective of this study was to use an innovative improvement to end‐member mixing analysis (EMMA) to identify time sequences of hydrologic processes affecting storm flow. Hydrologic and major ion chemical data from groundwater, soil water, precipitation and stream sites were collected over a 2‐year period at a watershed located in USDA Forest Service's Santee Experimental Forest near Charleston, South Carolina, USA. Stream flow was ephemeral and highly dependent on evapotranspiration rates and rainfall amount and intensity. Hydrograph separation for a series of storm events using EMMA allowed us to identify precipitation, riparian groundwater and streambed groundwater as main sources to stream flow, although source contribution varied as a function of antecedent soil moisture condition. Precipitation, as runoff, dominated stream flow during all storm events while riparian and streambed groundwater contributions varied and were mainly dependent on antecedent soil moisture condition. Sensitivity analyses examined the influence of 10% and 50% increases in analyte concentration on EMMA calculations and found that contribution estimates were very sensitive to changes in chemistry. This study has implications on the type of methodology used in traditional forms of EMMA research, particularly in the recognition and use of median end‐member water chemistry in hydrograph separation techniques. Potential effects of urban development on important hydrologic processes (groundwater recharge, interflow, runoff, etc.) that influence stream flow in these lowland watersheds were qualitatively examined. Copyright © 2011 John Wiley & Sons, Ltd.     

Coral microatoll as geodetic tool in North Andaman and Little Andaman,India

Coral microatolls were examined from North Andaman and Little Andaman to understand the relative sea level change due to vertical tectonic deformation above the subduction interface. The highest level of survival of coral microatoll before the 26 December, 2004 earthquake at eastern coast of North Andaman has been determined by Global Ocean Tide Model. The present position of recently dead flat top microatoll with preserved internal structure at the eastern coast of North Andaman mainland indicates 31.21 cm uplift due to the 26 December, 2004 earthquake. Comparatively old cup shaped microatoll at the eastern fringe of North Andaman group of islands and highly bioeroded fossil microatolls at the intertidal zone of Little Andaman bear the signature of permanent vertical deformation in the past.     

Hysteresis‐based flood‐wave analysis using the concept of strain

Hysteresis represents a loop in a rating curve and is a phenomenon which closely resembles that occurring in stress–strain curves used for studying the elastic properties of solid substances in engineering mechanics. Earlier hysteresis‐based studies used for defining floodwave propagation in open channels have qualitatively shown that hysteresis is an index of energy loss during floodwave propagation. Using the concept of elasticity, this paper introduces a new term called flow strain (defined as the ratio of change in discharge to the initial discharge) for investigating hysteresis. The usefulness of this new term is evaluated with use of four dam‐break studies. The study reveals that:

• 1 flow strain is a function of three wave speeds, Seddon speed, Lagrange speed, and elastic speed;
• 2 a single linear reservoir concept frequently used in flood routing is a specific variant of the Seddon speed formula;
• 3 the non‐linear storage–discharge relationship, widely used in overland flow modelling, is a variant of the kinematic wave representation;
• 4 the discharge ordinates on the recession part of a hydrograph follow a simple first‐order autoregressive form;
• 5 the hysteresis, phase difference and logarithmic decrement all define attenuation and are indices of energy loss during floodwave propagation.

Copyright © 2001 John Wiley & Sons, Ltd.     

Drainage basin peak discharge rating curve

The stream gauge rating curve for a drainage basin can be transformed into a drainage basin peak discharge rating curve that is more stable than the rating curve from which it is derived. The resulting drainage basin peak discharge rating curve can be used to predict peak discharge, identify anomalous discharges caused by channel obstructions or other causes, evaluate the effect of flood retarding structures, and evaluate historical records. The drainage basin peak discharge rating curve is valid for drainage basins of any size, for any discharge up to the time of concentration, and for snowmelt.     

Influence of regional and local topography on the distribution of polymetallic nodules in Central Indian Ocean Basin

Detailed bathymetric surveys from part of the Central Indian Ocean revealed several bathymetric features such as hills, slopes, valleys, and plains. Areas with a local relief of a few to hundreds of meters generally have a high abundance of polymetallic nodules with a patchy distribution. Areas with less relief have lesser abundance but a regular distribution. North-south topographic profiles have a smoother sea floor than the east-west ones. Near the minor faults, the abundance is high. Mn,Ni,Mn/Fe levels are higher in the plain areas, and rough terrains have high Fe,Co and low Mn/Fe levels.     

Environmental effects on grinding

The effect of surface-active agents in improving the grinding efficiency for haematite, expressed as a measure of reduction ratio, has been studied. Drying of the feed before grinding has been found to improve the grinding efficiency. The effect of surfactant additions on hardness, microhardness, crushing strength and wet grinding of haematite has shown that dispersants are better than flocculants, and each dispersant has a critical concentration at which the grinding efficiency is maximum.     

The distribution and growth of urban settlements in Saudi Arabia

This paper examines the distribution characteristics of urban settlements in the Kingdom of Saudi Arabia through major dimensions such as settlement regularly, degree of primacy and polarisation at the national and geographic regional levels. The paper points out that the settlement pattern at the national level has transformed from a primate distribution during the pre-plan period (< 1970) to an intermediary distribution during the period of development planning (1970 >). At the geographical regional level the settlement distribution, however, has shown diverse pattern. While the regional settlement distribution of Western and Eastern Region have shown trends of increasing polarisation, settlements in the Northern and Southern Regions are more log-normal in character. This is explained by the increasing growth of small and intermediary towns in the Northern and Southern Regions. The paper concludes that the national trend of decreasing urban primacy, induced by the decentralised national development strategies, is less pronounced due to the absence of a balanced regional investment policy. Since the government expenditure and settlement population growth rates are not related, slow growing primate cities continue to receive a larger share of public expenditure, enabling them to retain their primacy. This calls for a balanced regional investment policy to fully realise the national strategy of regional balance and multi-polar settlement pattern.