Establishment of a reedbed within a created surface water fed wetland nature reserve

In the early 1990's, outline designs for two wetland nature reserves were being prepared: the Teeside International Nature Reserve (TINR) and the Cardiff Bay Barrage Environmental Compensation Measures at Redwick, Gwent. The initial design for both proposals identified reedbed as a desirable habitat for establishment. The initial design works identified the importance of reedbed evapotranspiration [ET(Reed)] within the water budget, however, literature searches identified a paucity of information on this parameter. Field experiments for the measurement of ET(Reed) from Phragmites australis are described for three sites distributed across England and Wales. Reference Crop Evapotranspiration (ETo) was calculated using techniques recommended by the Food and Agriculture Organisation. A technique for the calculation of a reedbed crop coefficient [Kc(Reed)[, from ET(Reed) and ETo data is discussed. Kc(Reed) values produced in the project were found to be similar to those developed previously in continental Europe. Mean monthly and crop development stage Kc(Reed) values are presented which are applicable in the UK and possibly worldwide. A conceptual hydrological model of surface water fed reedbed systems is developed, and used to calculate the hydrological sustainability of reedbed creation areas in the UK. Finally, the water budget model is verified using data from a small clay catchment located on the TINR. In addition, a methodology is developed for the hydrological design of surface water fed reedbed systems, and recommendations required for the feasibility, design and establishment stage of reedbed creation sites. Further research needs are also identified.

Assessment of the impact of discharges from surface water sewers on receiving water quality

A broad based approach has been used to assess the impact of discharges to rivers from surface water sewers, with the primary objective of determining whether such discharges have a measurable impact on water quality. Three parameters, each reflecting the effects of intermittent pollution, were included in a field work programme of biological and chemical sampling and analysis which covered 47 sewer outfall sites. These parameters were the numbers and types of benthic macroinvertebrates upstream and downstream of the outfalls, the concentrations of metals in sediments, and the concentrations of metals in algae upstream and downstream of the outfalls. Information on the sewered catchments was collected from Local Authorities and by observation of the time of sampling, and includes catchment areas, land uses, evidence of connection to the foul system, and receiving water quality classification. The methods used for site selection, sampling, laboratory analysis and data analysis are fully described, and the survey results presented. Statistical and graphical analysis of the biological data, with the aid of BMWP scores, showed that there was a small but persistent fall in water quality downstream of the studied outfalls. Further analysis including the catchment information indicated that initial water quality, sewered catchment size, receiving stream size, and catchment land use were important factors in determining the impact. Finally, the survey results were used to produce guidelines for the estimation of surface water sewer discharge impacts from knowledge of the catchment characteristics, so that planning authorities can consider water quality when new drainage systems are designed.

A near real-time water surface detection method based on HSV transformation of MODIS multi-Spectral time series data

In the face of global population growth and the uneven distribution of water supply, a better knowledge of the spatial and temporal distribution of surface water resources is critical. Remote sensing provides a synoptic view of ongoing processes, which addresses the intricate nature of water surfaces and allows an assessment of the pressures placed on aquatic ecosystems. However, the main challenge in identifying water surfaces from remotely sensed data is the high variability of spectral signatures, both in space and time. In the last 10 years only a few operational methods have been proposed to map or monitor surface water at continental or global scale, and each of them show limitations. The objective of this study is to develop and demonstrate the adequacy of a generic multi-temporal and multi-spectral image analysis method to detect water surfaces automatically, and to monitor them in near-real-time. The proposed approach, based on a transformation of the RGB color space into HSV, provides dynamic information at the continental scale. The validation of the algorithm showed very few omission errors and no commission errors. It demonstrates the ability of the proposed algorithm to perform as effectively as human interpretation of the images. The validation of the permanent water surface product with an independent dataset derived from high resolution imagery, showed an accuracy of 91.5% and few commission errors. Potential applications of the proposed method have been identified and discussed. The methodology that has been developed 27 is generic: it can be applied to sensors with similar bands with good reliability, and minimal effort. Moreover, this experiment at continental scale showed that the methodology is efficient for a large range of environmental conditions. Additional preliminary tests over other continents indicate that the proposed methodology could also be applied at the global scale without too many difficulties