Abstract:Rainfall is the key climate variable that governs the spatial and temporal availability of water. In this study we identified monthly rainfall trends and their relation to the southern oscillation index (SOI) at ten rainfall stations across Australia covering all state capital cities. The nonparametric Mann-Kendall (MK) test was used for identifying significant trends. The trend free pre-whitening approach (TFPW) was used to remove the effects of serial correlation in the dataset. The trend beginning year was approximated using the cumulative summation (CUSUM) technique and the influence of the SOI was identified using graphical representations of the wavelet power spectrum (WPS). Decreasing trends of rainfall depth were observed at two stations, namely Perth airport for June and July rainfall starting in the 1970s and Sydney Observatory Hill for July rainfall starting in the 1930s. No significant trends were found in the Melbourne, Alice Springs and Townsville rainfall data. The remaining five stations showed increasing trends of monthly rainfall depth. The SOI was found to explain the increasing trends for the Adelaide (June) and Cairns (April) rainfall data and the decreasing trends for Sydney (July) rainfall. Other possible climatic factors affecting Australian rainfall are also discussed.

Spatial and temporal characteristics of rainfall in the United Arab Emirates (UAE) were investigated. The region is divided into four climate zones (East Coast, Mountains, Gravel Plains and Desert Foreland) of distinguished rainfall distribution. The rainfall patterns, rainfall probability of occurrences, rainfall intensity-duration-frequency (IDF) relationship, probable maximum precipitation (PMP) and drought scenarios were investigated. Daily rainfall data from a network of stations across the UAE were used. Standard statistical techniques were applied for data analyses. The Gumbel, log Pearson, generalized extreme value, log normal, Wakeby and Weibull probability distributions were tested to fit extreme rainfalls. Both Gumbel and Weibull distributions were found adequate. Measures of dispersion and symmetry of rainfall patterns were found relatively high. The estimated PMP values were found highest in the East Coast region and lowest in the Gravel Plains region. Estimated drought severity index showed that the regions have similar trends of drought patterns over the years. The study is useful for sustainable water resources planning and management in the region.

Selection of appropriate river water treatment methods is important for the restoration of river ecosystems. An in-depth review of different river water treatment technologies has been carried out in this study. Among the physical-engineering processes, aeration is an effective, sustainable and popular technique which increases microbial activity and degrades organic pollutants. Other engineering techniques (water diversion, mechanical algae removal, hydraulic structures and dredging) are effective as well, but they are cost intensive and detrimental to river ecosystems. Riverbank filtration is a natural, slow and self-sustainable process which does not pose any adverse effects. Chemical treatments are criticised for their short-term solution, high cost and potential for secondary pollution. Ecological engineering-based techniques are preferable due to their high economic, environmental and ecological benefits, their ease of maintenance and the fact that they are free from secondary pollution. Constructed wetlands, microbial dosing, ecological floating beds and biofilms technologies are the most widely applicable ecological techniques, although some variabilities are observed in their performances. Constructed wetlands perform well under low hydraulic and pollutant loads. Sequential constructed wetland floating bed systems can overcome this limitation. Ecological floating beds are highly recommended for their low cost, high effectiveness and optimum plant growth facilities.

ABSTRACT:Rainfall characteristics at different temporal resolutions play a significant role in sustainable urban water management. In this study we attempted to identify the temporal characteristics and variability of point rainfall measured in Melbourne, Australia. Statistical moments, lag1 autocorrelation, the Buishand's Q test for homogeneity, the Mann-Kendall (MK) test for trend and wavelet analyses for temporal variability were carried out for rainfall intensities at resolutions of 0.1, 0.5, 1, 3, 6, 12 h and for the monthly rainfall depths and proportion dry ratios. Series of rainfall intensities at different temporal scales and the monthly rainfall depths and proportion dry ratios were accumulated from the high resolution rainfall dataset for the period from 1925 to 2002. Homogeneity of rainfall intensity was found to increase as the temporal scale increases. Both rainfall intensities and monthly rainfall depths were found to be serially correlated. The 2nd, 3rd and 4th statistical moments of rainfall intensities increased as the resolution increased. While no statistically significant trends were found using the MK test, there were indications that trends are more likely as the temporal scale increases. Wavelet power spectra identified a dominant frequency scale (0.25-1 year) in the 3, 6 and 12 h rainfall intensities that were periodically observed in a 5 to 10-year cyclic order. This phenomenon could be influenced by the inter-annual variability of the El Niño Southern Oscillation (ENSO).

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