Climate change and its consequences present one of the most important threats to water resources systems which are vulnerable to such changes due to their limited adaptive capacity. Water resources in arid mountain regions, such as Al Jabal Al Akhdar; northern Sultanate of Oman, are vulnerable to the potential adverse impacts of environmental and climate change. Besides climatic change, current demographic trends, economic development and related land use changes are exerting pressures and have direct impacts on increasing demands for water resources and their vulnerability. In this study, vulnerability assessment was carried out using guidelines prepared by United Nations Environment Programme (UNEP) and Peking University to evaluate four components of the water resource system: water resources stress, water development pressure, ecological OPEN ACCESSWater 2014, 6 3119 health, and management capacity. The calculated vulnerability index (VI) was high, indicating that the water resources are experiencing levels of stress. Ecosystem deterioration was the dominant parameter and management capacity was the dominant category driving the vulnerability on water resources. The vulnerability assessment will support policy and decision makers in evaluating options to modify existing policies. It will also help in developing long-term strategic plans for climate change mitigation and adaptation measures and implement effective policies for sustainable water resources management, and therefore the sustenance of human wellbeing in the region.

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A field study was conducted to compare and evaluate chemical composition of soil water collected in sandy soils by three common methods: (i) ceramic suction cup sampling, (ii) drainage lysimetry, and (iii) gravimetric soil sampling. The ceramic cups were installed either by surrounding the cup with silica slurry or sand. The experiment was arranged as a nested factorial design where the three factors were: (i) sampling method, (ii) location, and (iii) time of sampling. Analysis of variance (ANOVA) was used for statistical analysis of data. The study shows that the method of installation (use of silica slurry vs. sand) of ceramic cups had a negligible effect on the mean values, but it appears that by using silica the uncertainty associated with the mean was 1677 ORDER REPRINTS reduced considerably. The average concentration of NO 3 and Cl were higher for soil sampling than those measured by ceramic cups. The mean values of NO 3 , PO 4 , and Cl were higher for ceramic cups than for lysimeter although differences proved statistically insignificant.

Summary Although cloud seeding is a commonly used and plausible method for rainfall enhancement, its practical efficacy has not been established for seeding of convective clouds with hygroscopic materials. Other methods of rainfall enhancement are viewed as much less plausible. Thus, although increased electrical charge has been shown to enhance precipitation in cloud chamber experiments, exactly how ionisation of clouds can increase rainfall in the open atmosphere remains conjectural. A trial of the efficacy of ionisation for rainfall enhancement in the Hajar Mountains of Oman was carried out over 2013–2018. This paper provides some background to this non‐mainstream approach to increasing rainfall, showing how statistical modelling of rainfall data might be used to nudge rainfall enhancement via ionisation towards a more scientifically acceptable status. Analysis of the data collected in the trial shows that ionisation led to a statistically significant enhancement in positive rainfall in gauges located up to 70 km downwind of the ionisers. A headline analysis specified prior to commencement of the trial resulted in an estimate of 16.23% enhancement relative to rainfall that would have fallen without any ionisation, while a more sophisticated after the event analysis increased this estimate to 17.64%.