Catchment water quality: the inconvenient but necessary truth of fractal functioning

This commentary concerns catchment water quality functioning in relation to environmental impact assessment, with a view to proposing that much more emphasis be placed on issues of within-catchment complexity and its manifestation within stream water chemistry: fractal dynamics. The commentary is based, with closure, on my long-term research. Encouragement is given for new avenues to be pursued, including dealing with the complexities of within-stream biological functioning, and their integration into environmental legislation

How to Unravel and Solve Soil Fertility Problems

Land Economics/Use,

Estimating nutrient concentrations from catchment characteristics across the UK

Within a Geographical Information System (GIS) framework, the distributions of nitrate and orthophosphate concentrations at monitoring sites across the UK were examined and empirical relationships with catchment characteristics were established. The mean orthophosphate concentrations were linked strongly with the urban component, and less significantly with effective rainfall and agricultural coverage. This is of strategic importance in relation to phosphorus and the Water Framework Directive. Correspondingly, mean nitrate concentrations were linked to land-use types, base flow index and effective rainfall. Within-catchment residence times and effective-rainfall (runoff) were important in relation to nitrate. The issue of nitrate and the Water Framework Directive is more complex than that for orthophosphate and involves a strong agricultural as well as an urban component

A Raycast Approach to Collision Avoidance in Sailing Robots

Abstract—This paper presents a simple mechanism for an autonomous sailing robot to detect when it is within close proximity to fixed obstacles and a reactive mechanism to avoid those obstacles. This is achieved by using a raster based map of the local area and raycasting from the boat’s current position in order to determine the distance and heading to the nearest coastline. Once this is determined a new target heading which does not result in any immediate danger is computed. Simulations have shown that it is possible for a robot to sailing between a set of waypoints while avoiding obstacles placed between those waypoints. This method has been shown to be capable of selecting a sensible course and avoiding collisions in most cases, however when the robot becomes trapped in small inlets or between groups of tightly packed islands it can fail to find a suitable course. I