Bart Schultz

Water rights and rules, and management in spate irrigation systems in Eritrea, Yemen and Pakistan

Spate irrigation is a system of harvesting and managing flood water. In spate irrigation, flood water is emitted from wadis (ephemeral streams) and diverted to fields using earthen or concrete structures. By nature, flood water is unpredictable in occurrence, timing and volume, which puts special challenges to the farmers who use, co-share and co-manage the resource. Primarily based on the research conducted in spate irrigation systems in Eritrea, Yemen and Pakistan, this chapter discusses the interlinkage between local flood water management and water rights and rules, and the enforcement mechanisms in place. It assesses how formal national/provincial land and water laws affect local flood water management and argues that what matters most are the local rules for cooperation and sharing the resource and, hence, that formal water and land rights for spate irrigation should recognize local water rights and management.

Comparative non-linear regression - case of infiltration rate increase from upstream in valley

Abstract In Tropical Savannah flooded valley soils, very low infiltration rates often result in acidic conditions favourable to high concentrations of metallic ions, toxic for rice. Determination of the under-phreatic infiltration rate is important in drainage design to reclaim degraded soils. Several studies have addressed the mapping of the infiltration rate. Yet, its relationship with the toposequence of the valley is not clarified. This paper has investigated such a possibility, examining the case of the irrigated rice valley of Tiefora, Burkina Faso. Nine boreholes – from 1 to 5 m deep – were implemented from upstream to downstream. The Lefranc permeability test of the under-phreatic level in waterlogged soils – used when the impervious layer is close to soil surface or absent – was conducted. First, a comparative regression was applied to the data, including all the parameters of the regression curves. In the case of dissimilarity of the infiltration processes, the comparison focused on the final permeability. The results show a permeability increase from upstream (0.10±0.10cmh-1)todownstream (greater than 20±10 cm h-1 in some places). Taking into account such a permeability increase in the subsurface drainage system design would result in implementation of more efficient and cost effective systems.

Water management and flood protection of the polders in the Netherlands under the impact of climate change and man-induced changes in land use

Water management and flood protection of the polders in the Netherlands under the impact of climate change and man-induced changes in land use Two-third of the area of the Netherlands is flood prone. Storm surges at the North Sea, floods in the rivers, failure of secondary dikes, as well as heavy rainfall may cause flooding. Most of the flood prone areas rely for their existence on drainage by pumping, because their surface level may be permanently or during floods up to several metres below the surrounding water levels. During the past decades climate change is generally felt as a reason for major concern. However, the impacts of climate change on increase in extreme conditions may be up to 45% per century. If we look at the man-induced changes in land use, due to increase in population and rapid increase in the value of public and private property, then one may observe an increase of 100-1,000% per century. One should therefore wonder what would have to be our major concern. In the paper the relevant processes are described, based on some characteristic data on water management and flood protection in the Netherlands. It is shown that impacts of climate change on water management and flood protection may be expected, but that such impacts can easily be accommodated during improvement works on water management systems and flood protection provisions that from time to time will be required. It will be much more important to take carefully into account the risk of flooding in the planning of land use development, especially for valuable types of land use like urban and industrial areas, green houses and recreation areas. Gospodarowanie wodą i ochrona polderów przed powodzią w Holandii w aspekcie globalnych zmian klimatu oraz antropogenicznych zmian użytkowania ziemi Dwie trzecie powierzchni Holandii jest narażonych na powodzie. Sztormowe spiętrzenia wód na Morzu Północnym, wysokie stany wody w rzekach, awarie obwałowań rowów czy obfite opady mogą powodować powodzie. Użytkowanie obszarów narażonych na zalewanie zależy od stałego odwodnienia i od pompowania wód, ponieważ ich powierzchnia może (trwale lub tylko w czasie zalewu) znajdować się do kilku metrów poniżej poziomu otaczających wód. W ciągu ostatnich dziesięcioleci zmiany klimatu są postrzegane jako główny powód do niepokoju. Jednakże, wpływ zmiany klimatu może spowodować straty w wyniku wzrostu zjawisk ekstremalnych do 45% na stulecie. Jeśli spojrzymy na wywołane przez człowieka zmiany w użytkowaniu ziemi spowodowane przyrostem zaludnienia i gwałtownym wzrostem wartości infrastruktury to stwierdzimy, że przyrost strost może wynieść od 100 do 1000% na stulecie. W związku z tym należy zapytać, co powinno być przedmiotem naszej szczególnej troski? W oparciu o charakterystyczne dane dotyczące gospodarki wodnej i ochrony przeciwpowodziowej w Holandii opisano w pracy wyniki analiz prognostycznych. Wykazano, że można oczekiwać wpływów zmian klimatu na gospodarkę wodną i ochronę przeciwpowodziową, ale te wpływy dadzą się łatwo uwzględnić przy pracach związanych z usprawnianiem systemów gospodarki wodnej czy środków ochrony przeciwpowodziowej, które od czasu do czasu trzeba będzie podejmować. Daleko bardziej istotne będzie zwrócenie szczególnej uwagi na ryzyko powodziowe w planowaniu przestrzennym, zwłaszcza w odniesieniu do zagospodarowania cennych obszarów takich jak tereny miejskie czy przemysłowe, obiekty ekologiczne czy tereny rekreacyjne.