Challenges for water sustainability in Africa
Water lies at the heart of many of Africa's problems. Although Africa as a whole is only slightly below the world average in terms of the available water resources per capita, and better off than Europe or Asia, it is beset by three critical groups of problem, one largely natural, the second very definitely manmade, the third somewhere in-between. The first centres on the distribution and reliability of resources. The second is related to the distribution and growth in human population. The third is the intimate link between water and disease in Africa, and the widespread lack of access to safe drinking water amongst the poorer communities. Much of the water that is theoretically available is either naturally dangerous for human health or else polluted by human activities lack of sewage treatment or pollution from agriculture, mining and industry. Despite the WHO's International Drinking Water Supply and Sanitation Decade in the 1980s, and the WHO's continuing Water, Sanitation and Health activities, the numbers without access to safe water continue to grow (WHO, 2004 website). Over 300 million still lack access to safe water in sub-Saharan Africa. Lack of access to safe water is worst in rural areas, where women and children often spend considerable time fetching water: over 1 .2 billion people worldwide live more than 1 5 min walk from a safe water source, many in Africa (Rodda, 1994). In the Southern African Development Community, 56% of rural communities lack access to safe water, against only 22% in urban areas. High temperatures favour the proliferation of many microbes as well as vectors of disease like the Anopheles mosquito. It is estimated that if malaria had been properly tackled 30 years ago when effective control measures first became available, Africa's GDP would now be about $100 billion greater (World Health Organisation, 2001). Public health is, therefore, not solely a question of safe water provision, but also of sound management of the water environment in order to control all water-related disease. Together, these factors make the average per capita water resource statistic largely meaningless in practical terms. Africa's climatic location is a fundamental source of its problems. Straggling the equator and extending beyond both tropics, the climates of Africa are dominated by the Hadley Cells. These circulation cells create both the excessive rains on the rising limb along the Intertropical Convergence Zone around the equator and the desiccation of the adiabatically heated air on the sinking limb around the subtropics, which suppresses convective activity and rain formation. This results in a grossly uneven distribution of water resources, ranging from desert to equatorial rainforest. Fluctuations in the strength of the Hadley Cells, their associated monsoons and other elements of atmospheric circulation in the tropics, like the Biennial Oscillation and the Southern Oscillation, also result in considerable and often critical unreliability of rainfall throughout much of the continent. To this is now being added clearly discernable climatic change, some perhaps natural, some apparently related to human-induced global warming. The frequency of drought appears to have increased in recent decades, particularly in the Sahel and the Horn of Africa. Drought in tropical Africa is often associated with the reversals of ocean currents in the equatorial Pacific known as El Nino, which have been getting more intense in recent years. At the same time, there have been some unusually intense tropical cyclones emanating from the western side of the Indian Ocean in the southern hemisphere. The hurricane seasons in 1999-2001 were especially problematic: the worst event for 50 years occurred between January and March 2000, when Cyclones Eline, Gloria and Hudah saw 150,000 ha flooded in Mozambique, hundreds killed and over 1 .25 million made homeless in southern Africa, including Botswana, South Africa, Zambia, Zimbabwe and Madagascar. There are, however, some more purely human elements in the increasing frequencies of droughts and flood disasters. Overgrazing, deforestation and devegetation have created long-term changes in the water balance of many desert margins, increasing the proportion of rainfall draining away as storm runoff, thereby increasing flood problems, eroding the top soil, reducing soil moisture retention and decreasing the recharge of aquifers. The eminent climatologist, Reid Bryson, has even suggested that increased dust from agricultural activity in semiarid regions has increased the atmospheric albedo or reflectivity, cooling the upper air and so inducing air subsidence which suppresses potentially rain-creating convective cells even further (Bryson and Murray, 1977). The net result has been that the West African monsoon has penetrated less far northwards into the Sahel in recent decades, aggravating the incidence of drought and famine. Similarly, the devastating Nile floods of 1988 were created by a combination of the 1000-year rainfall event and more rapid runoff caused by deforestation in the headwaters. Floods like these also carry risks for public health, increasing the incidence of diarrhoea, dysentery, cholera
Icebergs as a Fresh-Water Source: An Appraisal
Abstract A history of the idea of transporting large icebergs to arid regions to provide a fresh-water source is presented and the problem is considered in four main parts: (1) Location of a supply of icebergs. Only in the Antarctic are supplies of large tabular icebergs available. Data on the size distribution of these icebergs are reviewed and it is concluded that icebergs of almost any desired size can readily be located. (2) Towing. Steady-state towing velocities of different sized icebergs are calculated based on estimates of the drag of the icebergs and the bollard pull of tugs. Because drag increases with velocity squared, large icebergs can only be towed at very slow velocities (<c. 0.5 m/s). However, tugs that can be built within the capabilities of current technology are capable of towing extremely large icebergs. (3) Melting in transit. Calculations of melting indicate that, although melting losses are significant and may be excessive for small icebergs, when large icebergs are towed, large amounts of ice are left when the iceberg arrives at its destination. Towing trajectories, travel times, and ice delivery rates are calculated for optimum routes between the Amery Ice Shelf and Western Australia (A–A) and the Ross Ice Shelf and the Atacama Desert (R–A). Forces included in these calculations are towing, air, water, gradient current and Coriolis. Transit times exceed 107 d (A–A) and 145 d (R–A) with over 50% of the initial ice delivered. (4) Economic feasibility. After total towing charges are paid, it is possible to deliver ice to Western Australia for 1.3 mills/m3 of water and to the Atacama Desert region for 1.9 mills/m3. These costs are appreciably less than the expected price of water delivered at these locations (8 mills/m3). The water delivered by the operation of one super-tug alone would irrigate 16 000 km2. Problems related to both iceberg transport and processing are reviewed and although substantial problems do exist, they appear to be within the capabilities of current technology. It is suggested that the overall idea is indeed feasible and should be explored further by specific groups of experts.
List of the described Coleoptera ofTasmania.
The Coleoptera of Tasmania have never been considered as 
a whole since the time of Erichson, and no list or 
catalogue of the species has ever been compiled. About 
10,000 species have now been recorded from Australia and 
Tasmania, of which scarcely 400 have been described from 
Tasmania. A very imperfect knowledge of what species 
are confined to the island exists, as species supposed only 
to occur there, are constantly being found in Victoria and 
New South Wales, and even sometimes in Western Australia 
and Queensland; on the other hand, Tasmanian 
collectors frequently obtain mainland species which have 
never been recorded from Tasmania. 
I have considered it advisable, therefore, to prepare a 
list of the species hitherto recorded from Tasmania, adding 
to the list such species as I have seen in Tasmanian collections, 
or have myself taken in Tasmania. In this list, 
the genera and families are placed as far as possible in the 
order in which they appear in Masters' "Catalogue of the 
Described Coleoptera of Australia;" the species are placed 
alphabetically. All known synonyms have been omitted.