Quantifying flows along hydrological pathways by applying a new filtering algorithm in conjunction with master recession curve analysis

Quantifying the proportion of the river hydrograph derived from the different hydrological pathways is essential for understanding the behaviour of a catchment. This paper describes a new approach using the output from master recession curve analysis to inform a new algorithm based on the Lyne and Hollick ‘one‐parameter’ signal analysis filtering algorithm. This approach was applied to six catchments (including two subcatchments of these) in Ireland. The conceptual model for each catchment consists of four main flow pathways: overland flow, interflow, shallow groundwater and deep groundwater. The results were compared with those of the master recession curve analysis, a recharge coefficient approach developed in Ireland and the semi‐distributed, lumped and deterministic hydrological model Nedbør‐Afstrømings‐Model. The new algorithm removes the ‘free variable’ aspect that is typically associated with filtering algorithms and provides a means of estimating the contribution of each pathway that is consistent with the results of hydrograph separation in catchments that are dominated by quick response pathways. These types of catchments are underlain by poorly productive aquifers that are not capable of providing large baseflows in the river. Such aquifers underlie over 73% of Ireland, ensuring that this new algorithm is applicable in the majority of catchments in Ireland and potentially in those catchments internationally that are strongly influenced by the quick‐responding hydrological pathways. Copyright © 2013 John Wiley & Sons, Ltd.     

Distribution of coastal cliffs in Kerala,India: their mechanisms of failure and related human engineering response

The 560-km-long Kerala coast is characterised by long barriers with narrow beaches and steep cliffs. Distribution of cliffs from nine sections measuring a cumulative length of 63.5 km is evaluated in ArcGIS Software using topomaps and field survey data. The cliff sections in the southern coast comprise both permeable and impermeable rocks, whereas those along northern coast are comprised of either Precambrian crystalline and/or Tertiary formations. Notches, caves and even small arches are developed in Cannanore, Dharmadam and Kadalundi cliffs, where only primary laterites are exposed to wave attack. Stacks composed of laterite and Precambrian crystallines found in nearshore of cliffed coast indicate recession of shoreline. Mass wasting, mudslide and mudflow type of cliff failures are common in permeable to semi-permeable rocks, whereas rotational sliding, rockfall and toppling failure are found in hard rock cliffs. Retreat of cliff sections are induced by natural or anthropogenic activities or both. Rate of recession vary from a few centimetres to one metre/year depending upon the nature of lithology, structures and recession agents acting upon the cliffs. Various methods of cliff protection for e.g. hard structures—revetments, groins, seawalls, breakwater and jetties—and soft measures—artificial reefs/marsh creation, floating breakwaters, beach nourishment, beach scraping and vegetation planting—are suggested.     

What has happened in Spain? The real estate bubble,corruption and housing development: A view from the local level

How have the recent real estate, mortgage and financial crises affected different countries, territories and cities? How have the different public and private stakeholders behaved and how accountable have they been for the origin and development thereof? What links are there among the local, national and global contexts in the crises? Recent geographic research ought to attempt to answer these questions, but there have, however, been few in-depth studies on the link between urbanisation, financial markets and the global crisis. The present paper analyses one of the principal causes of Spain’s recent evolution: urbanisation of the territory, the start and consequences of housing bubble; our study emphasises the differential elements in relation to the crisis in other countries. We study in greater depth the municipality of Torrelodones, which constitutes a reference due to the appearance of a residents’ movement opposed to the development process and which is a perfect example of the dynamics that led to the economic and social crisis. We describe in detail the lack of any strategic vision, participation or transparency in town planning decision-making, the processes by which reports and inspections were doctored, and the mechanisms of corruption of public decision-making in town planning. Finally, we analyse the concrete manner in which huge losses in mortgage markets occurred, with the collapse of the real estate bubble and the financial markets, which subsequently forced a State bailout.     

Some aspects of the hydrology of one-day annual minimum low flows of malawian rivers

Five aspects of the hydrology of one-day annual minimum flows Q_IM, have been studied using data from twelve catchments in Malawi. Results indicate that the log-normal distribution can be fitted to all twelve catchments. Four of the rivers studied are intermittent. Application of statistical methods developed in meterology to the dichotomous-transformed data of these catchments revealed that two are ‘flow-dominant’ and the other two are ‘dry-dominant’. Another catchment is entirely dominated by a hydraulic gradient towards the Shire River and Elphant Marsh and so dries up every dry season for considerable periods of time despite the relatively high rainfall in the catchment. Q_IM, t-days after the date of occurrence of Q_IM(May), can be better estimated from simple regression than from an empirically determined recession constant.     

An improved method for delineating source protection zones for karst springs based on analysis of recession curve data

A standard method for delineating source protection zones, particularly for karst and carbonate springs, has been improved. The method, based on recession curve analysis, defines four vulnerability scenarios with an evaluation of the appropriate dimensions of the protection areas, accommodating situations where field-test data are not available. The new approach makes it easier to separate the components of the spring discharge hydrograph. The objective is to achieve simplification, and an effective, more rigorous, procedure in the determination of the parameters used by Mangin’s model—Mangin A (1975) Contribution a l’étude hydrodynamique des aquifères karstiques-Troisieme partie: Constitution et fonctionnement des aquifères karstiques (Contribution to the hydrodynamic study of karst aquifers, part 3: formation and work of karst aquifers). Ann Speleol 30(1):21–124. The original procedure, plus the lack of sufficient data, was open to subjective interpretation. With the aid of modern technology, a very large quantity of data is now available and it is necessary to process it using denoise type computer-based filters before passing to interpretation. Working with discharge data series, a statistical approach is proposed to give an analytical solution for determining the values of fundamental parameters of the recession curve model. The new procedure is defined and compared with the original methodology. The new approach has been tested and applied to a number of karst springs in Italy. A case history for a spring located in the Piedmont region of the Maritime Alps, is presented. The proposed new procedure can be utilised to mark the limits of the protection zones of tapped groundwater supplied for potable use, as required by European and local legislation.     

Numerical analysis and evaluation of groundwater recession in a flood detention basin

This study analyzes the groundwater environment in the Yangzhuang flood detention basin in Henan Province, China. A numerical model of groundwater flow is established based on the hydrogeological conditions in the basin and changes of groundwater level in the flood detention basin under flood detention and recession conditions. The results show that during flood diversion and storage, the groundwater level in the basin rises, mainly in four flood detention zones, with a maximum rise of 1.0 m. After the floodwater recedes, the groundwater level slowly drops in the detention basin along with flood discharge, finally returning to its original level fifty days later. This study indicates that groundwater recession in the flood detention basin is a slow process, where the rise of groundwater level may cause environmental problems such as soil swamping.     

Analysing individual recession events: sensitivity of parameter determination to the calculation procedure

ABSTRACT

This study assesses the sensitivity to model fitting methods and segment selection of the estimated parameters A and B of the model dQ/dt = ?AQ^B for individual events. We investigated about 750 recession events observed at 25 US Geological Survey gauges in the Iowa and Cedar river basins in the United States, with drainage areas ranging from 7 to 17 000 km². The parameters of these recession events were estimated using three commonly adopted methods and recession segments with different extraction criteria. The results showed that the variations of the parameter estimates for the same recession event were comparable to the variations of parameters between different events due to using different model fitting methods and recession segments. This raises cautions for comparative analysis of individual recessions. The result also implies that the nonlinear direct fitting method is the most robust among the three model fitting methods compared.

EDITOR Z.W. Kundzewicz ASSOCIATE EDITOR T. Okruszko     

Evaluation of karstic aquifers contribution to streams by the statistical analysis of recession curves

Karstic aquifers significantly contribute to streams in most of Turkey’s river basins, so studies on karst water resources have great importance for Turkey. Karstic aquifer contributions are generally emerging at several locations near the river bed and are not readily measured by direct hydrometric methods. In this study, the extent of karstic aquifer contributions to a stream will be investigated by the statistical analysis of recession coefficients of recession curves. Six stream gauging stations on different streams in the western Mediterranean region of Turkey are selected. Recession periods of the streams are simulated by exponential and quadratic recession curve models. Recession coefficient series of the stream gauging stations are statistically investigated. The comparison of various statistical parameters shows that the recession coefficient series are fairly related to the karstic aquifer contributions. Especially, the measure of spread parameters, standard deviation and interquartile range of recession coefficient series are related to the extent of the karstic aquifer contributions to streams.