Bruce Lankford

The Sustainable Coexistence of Wetlands and Rice Irrigation: A Case Study from Tanzania:

An existing United Kingdom–funded water project, located in the Usangu Plains of Tanzania, aims to understand the causes for dry season zero flows in the previously perennially flowing Great Ruaha River, which drains from the Usangu wetland. Studies reveal that the common explanation of competition for water between wetlands and irrigation alone is insufficient to explain reduced flows. Instead, complex biological and hydrological processes influence the allocation of water between wetlands and irrigation. This article outlines these processes and proposes some hypotheses: (a) Certain types of rice irrigation development may not be detrimental to the Usangu wetlands; (b) the sustainability of rice irrigation and wetlands can be supported by recognizing their dynamic nature; (c) the concept of efficiency of irrigation in areas with a semiarid climate should be treated with caution. The studies will assist in the sustainable management of water for both environmental and developmental needs.

Does Article 6 (Factors Relevant to Equitable and Reasonable Utilization) in the UN Watercourses Convention misdirect riparian countries

The “factors relevant to equitable and reasonable utilization” of a watercourse expressed in Article 6 of the UN Watercourses Convention were incorporated into an Excel model using an analytical hierarchy process to examine how the article guides water allocation between countries within transboundary basins. This model was employed in training from 2008 to 2011 with scientists from transboundary basins including the Limpopo and Zambezi Rivers. Contrasting these results with those from a model designed to explore water sharing from a sectoral-growth perspective indicates that Article 6, in its current formulation, cannot guide adjustments to current water shares between countries.

Hydrological modelling of water allocation, ecosystem services and poverty alleviation in the Pongola floodplain, South Africa

The Pongola River Ecosystem Services for Poverty Alleviation (PRESPA) project quantified the economic benefits accuring to different livelihood sectors from the water resources of the Pongola floodplain, South Africa. The floodplain carries a diverse economy and ecology which is supported by flood events that once occured naturally but are now regulated by an upstream dam. PRESPA modelled the eco-hydrology which underpins various ecosystem services to determine how this might be managed to alleviate poverty. A model was used to quantify the economic value of the available water, especially the value accruing to the poor. This model linked to three development scenarios to explore trade-offs and outcomes of (1) a status quo, ‘unstructured’ economy; (2) a structured diverse economy; and (3) a structured ‘single sector’ agricultural economy. This model gives decision makers a measure of where water is best used in terms of poverty alleviation and enables them to examine future economic and ecosystem trajectories. In summary, poor households on the floodplain currently have a diversity of income and food sources, making them less vulnerable to economic and climatic shocks, while there is a trend towards intensive agriculture which may deliver higher returns but with greater costs and increased vulnerability.

The impact of design approximations on the operational performance of an irrigation scheme

A method is presented to analyse the impact of the selection of irrigation gates on operational performance of the Sungai Muda Irrigation Scheme in Malayisa. The method examines the discharge capacity of the water control gates at all levels in order to compare the specific water supply (the ratio of supply to command area) with the specific water demand which is the required hydromodule. The term hydromodule is the reciprocal of “water duty” and thus has units of litres/second/hectare. The greater the deviation between the two, the greater the potential loss of control during the operation of the scheme. The method is relatively simple but is more complex in this particular example as two hydromodules are used for the irrigation of basin rice; one for the presaturation period and one for the normal supply period. The most common cause of loss of water control is found to be provision of oversized turnout gates at the head of secondary and tertiary canals. Such design approximations enable more water to be used in those command areas thus leading to waste and to shortage of water in other areas. It is suggested that during design and rehabilitation of irrigation schemes, the operational implications of design approximations should be examined more carefully.

Hydrological modelling to assist water management in the Usangu wetlands, Tanzania

Abstract The Usangu wetlands, containing the Ihefu swamp, are one of the most valuable inland wetlands in Tanzania. Over the last decade, outflow from the swamp has ceased for extended periods in the dry season. This has had severe consequences for downstream ecosystems, including the Ruaha National Park. Results from a simple hydrological model developed for the Ihefu swamp indicate that, between 1958 and 2004, dry season inflows declined by approximately 60% and the dry season area of the swamp decreased by approximately 40% (i.e. from 160 km2 to 93 km2). The model also shows that to maintain minimum downstream environmental flows requires a minimum inflow of 7 m3s‐1, which is approximately 65% greater than occurs currently. There is significant potential for improving water use efficiency. However, given the socio‐economic importance of current levels of water withdrawal, this inflow may be difficult to achieve. Consequently consideration needs to be given to other options, including upstream storage and water management within the wetland itself. This paper highlights that a simple model supplying relatively low‐confidence, but indicative, results can provide a useful basis for contemplating water management options.

Water rights and water fees in rural Tanzania

In Molle, Francois; Berkoff, J. (Eds.). Irrigation water pricing: the gap between theory and practice. Wallingford, UK: CABIComprehensive Assessment of Water Management in Agriculture Series 4

A legal-infrastructural framework for catchment apportionment

We propose a water management framework for bringing together formal and informal water rights and irrigation intake design to apportion water in catchments. This framework is based on setting and modifying seasonally applied volumetric and proportional caps for managing irrigation abstractions and sharing water between upstream irrigators and downstream users in river basins. The volumetric cap, which establishes the upper ceiling of irrigation abstractions in the wet season, relates to formal water rights and maximum intake capacities. The proportional cap, which functions in the dry season beneath the volumetric ceiling, builds on customary water negotiations and on the design and continual adjustment of intakes by users. Both caps should be viewed as being adjustable in response to dialogue between users. The analysis is informed by conditions found in the Great Ruaha river basin, southern Tanzania, where rivers sequentially provide water for irrigation, a wetland, the Ruaha National Park and for electricity generation. Consequences for catchment interventions in the face of climate, population and land use change are explored.

The use of measured water flows in furrow irrigation management — a case study in Swaziland

The use of measured water in controlling flows for the irrigation of sugarcane was found to be vital for the rehabilitation and management of surface irrigation on a 5000 ha sugarcane project. Methods of water delivery, measurement and control at Inyoni Yami Swaziland Irrigation Scheme (IYSIS) are described. Improvements to the irrigation, using existing methods of water measurement, were carried out over a period of four years. The lessons gained in this programme of improvements confirmed the benefits of using modulus gates which allow a constant, measured, discharge of water.

A Water Perspective on Land Competition

This chapter reflects on land competition from a water perspective. Conceptual thoughts are enriched with evidence drawn from case studies as well as other published studies about both land and water. At the same time, it lays down an analytical framework for these case studies. Starting with a discussion of the inherent relationship between land and water, we explore recent disconnects in land and water studies that make it difficult to collate empirical evidence and comprehensive understanding of how competition between water and land are inherently linked. For us the term competition refers to gaining access to or control over—either land or water—and thus simultaneously captures social and material dimensions. To address these linkages, we employ the concept of waterscapes. One way of seeing waterscapes is through the lens of the competition that occurs at specific places, in various positions and on/across various scales, thereby capturing a combined view of land and water. The notion of waterscapes is mainly used by scholars from the fields of political ecology and critical geography thinking to explore how power is wielded, and in determining when and where who or what gets how much water/land. We briefly review the different notions of competition in disconnected literature concerning land and water in order to instil a further analytical dimension: whilst the term “competition” is increasingly used in land change science to refer to the global rush for land, water scholars refer rather to the various means of water governance.