A catchment model, which has the objective of simulating streamflow and calculating groundwater recharge of a small undeveloped catchment «100 km2), is described. The model accepts input daily data of rainfall and potential evapotranspiration, and it consists of two parts. Firstly, the modified Stanford Model to simulate the land phase processes, and secondly the Penman-Grindley soil moisture balance to calculate recharge. Several assumptions have been made so that the model can be applied on a rural catchment from which rainfall data is routinely collected on a daily basis. In order to estimate recharge accurately the volumes of interception and surface runoff have to be estimated first. This is done by the modified Stanford Model. The root constant parameter in the Penman-Grindley soil moisture balance provides a realistic formulation for recharge calculations. The root constant is easily estimated from the crop cover and hence can be used to simulate the effect of changing land use on the hydrologic regime. The model has been developed on a small catchment (63 km 2 ) of the River Bain above Goulceby in East Lincolnshire. Simulation of streamflow is indicated to be more accurate in the low- to medium flow ranges than in the high flow range. Although the time step of one-day adopted in the rr.odel is sufficient for accurate calculation of recharge, it is not sufficient for accurate simulation of surface runoff which characterises the high flow events. In addition to simulation of recharge and streamflow, the model can also be used to study the effect of variation of certain parameter on the hydrologic regime.

No description available.

No description available.

This research has endeavoured to characterise soil water flow vectors across a distribution of plots within two undistributed tropical rain forest catchments in Southeast Asia. The research focused on the potentially contrasting flow pathways through two different soil types: the Ferric Acrisol of the Jungle Falls catchment (Singapore), and the Haplic Alisol of the W8S5 catchment (Sabah, Malaysia). The research also sought to determine the uncertainty associated with the flow characterisation methodologies. Flow pathways were determined using two quite separate techniques within each experimental plot. A traditional Darcy-approach (i.e. use of the Darcy-Buckingham equation) was used in combination with an artificial tracer approach, to determine if sound flow predictions can be made from local measurements of hydraulic conductivity and capillary potential. Analysis of the results indicates that the flow pathways within the two soils contrasted markedly. Tracer evidence suggests that soil water movement within the Ferric Acrisol (Jungle Falls catchment) was predominantly vertical. In the Haplic Alisol (W8S5 catchment), the dominant flow pathway of the tracer was laterally though A and B1 horizons. Often rapid tracer breakthrough velocities were observed, which exceeded the measured soil saturated hydraulic conductivity by several orders of magnitude. This infers the macropores are an important flow route within both the Ferri Acrisol and the Haplic Alisol. In general, the Darcy-based approach failed to predict the velocity and dominant pattern of the tracer flows. This resulted from problems associated with the measurement of the soil parameters needed to solve the Darcy-Buckingham equation. Uncertainty analysis of the measurement and empirical techniques used to derive the Darcy-Buckingham equation parameters indicated that there is serious potential for error, particularly in the derivation of saturated hydraulic conductivity.

This thesis describes an investigation of the flood response of Burnes Gill and Force Beck, two upland catchments in the North West Pennines. The objectives of the study were to examine whetler an understanding of the catchment processes which generate flood runoff can be used to improve the structure of existing flood estimation techniques or their. application at the ungauged site. Rainfall, discharge and soil moisture were measured over a period of two years on two small catchments with contrasting topography and geology. Flood response was defined by the magnitude and volume of separated discharge and related to rainfall depth, intensity and several direct and indirect estimates of catchment wetness. The average response was lower and less dependent on antecedent wetness on Burnes Gill, one of the steepest gauged catchments in the United Kingdom than on the flatter Force Beck catchment. This difference in response was related to the contributing areas of the two catchments, defined by neutron probe measurements and field survey. The implications of these results for flood estimation at the ungauged site in the United Kingdom are illustrated by considering the Transport and Road Research Laboratory and Flood Studies Report flood design techniques.

No description available.

No description available.

Surface interpolation and, more particularly isarlthm interpolation are common procedures in the Earth Sciences and increasingly common ones in most other disciplines. Data for such Interpolation are increasingly being stored in a computer-accessible form as a prerequisite to a computer-derived solution. This has resulted in the development of a large assortment of computer software to perform the interpolation. The scientist is thus faced with a predicament of which is the optimum method of isarlthm interpolation for his data- This thesis describes an empirical evaluation of the performances of a comprehensive selection of software in relation to data characteristics. Much of the software is available in the academic environment or was developed by the author. The evaluation utilises detailed, photogrammetrically derived digital terrain data which are related to some currently used data classification systems. Additionally, several techniques, mostly derived from geomorphometry, are used to examine the data in more depth, in an attempt to establish reliable descriptors of their data characteristics. These descriptors are designed to be used in a multi-disciplinary environment. The interpolation process is essentially classified into three stages for evaluation. Random-to-grid algorithms are evaluated by considering the interpolated grid in relation to an observed grid. Grid-to-isarithm and random-to-isarithm interpolation are evaluated by considering the interpolated Isarithms with observed isarithms. In both cases, geometric errors and the morphological trueness of the interpolation product are considered using graphical and numerical parameters. These statements of accuracy are correlated with the data characteristics to establish the main factors influencing isarithm interpolation.

No description available.

No description available.