Upstream Water Use Research Articles

Coping with drought in irrigated South India: Farmers’ adjustments in Nagarjuna Sagar

Abstract Continuous upstream water development in the South Indian Krishna Basin has resulted in declining water availability downstream. Upstream water use is not adjusted to reflect rainfall fluctuations, and downstream farmers of the Nagarjuna Sagar irrigation project in the state of Andhra Pradesh are increasingly vulnerable to water supply shocks. Understanding the adaptive capacity of irrigated command areas to fluctuating water conditions is critical. This paper documents the wide range of adjustments adopted by managers and farmers in Nagarjuna Sagar during a period of fluctuating water availability (2000–2007). Primary and secondary data indicate managerial adjustments such as rotational and timely water supplies to meet critical water demands of standing crops. Farmers responded to changing conditions through: (a) crop diversification, (b) shifting calendars, (c) conjunctive use, (d) suspending cultivation, (e) sale of livestock, (f) out-migration, and (g) tampering with the irrigation system. Adaptive strategies are more diverse in the tail-end than in the head-end of the canal network and local adjustments are often uncoordinated and may degrade the resource base. A better understanding of the practices induced by changes in water availability is needed to refine current water allocation and management in large surface irrigation projects. Crop diversification, deficit irrigation in low-flow years, and conjunctive use are some of the practices to be promoted in a conducive agricultural environment.

Feedbacks on convection from an African wetland

The Niger Inland Delta in Mali floods every year in response to rain falling hundreds of kilometers upstream. This study examines the remote hydrological feedback between rainfall, fluvial inundation, and new convective storms. A satellite thermal infra‐red dataset spanning 24 years is used to quantify both temporal variability in wetland extent, and the response of cloud cover to the wetland during August and September. The daytime initiation of convective storms is found to double during periods of inundation, consistent with a hypothesised “wetland breeze” effect. A signal of enhanced cloud cover propagates hundreds of kilometers westwards, linked to increased numbers of long‐lived Mesoscale Convective Systems emanating from the wetland region. This effect raises the possibility that changes in upstream water use could have a climatic impact over a wide area.

Colorado River Floods, Droughts, and Shrimp Fishing in the Upper Gulf of California, Mexico

Accurate procedures that measure hydrologic variability would have great value for evaluating ecosystem impacts of upstream water use in the Colorado River Basin. Many local extractive income-based stakeholders rely directly or indirectly on ecosystem health and are adversely affected when the river does not flow. This study focuses on the impact of little or no Colorado River flow on the Mexican shrimp industry. Although there have been complaints that U.S. diversions of Colorado River flow have greatly impaired the shrimp fishery, this research demonstrates that freshwater rarely reaches the Gulf even during times of flooding, and that other factors such as overfishing may influence the instability of shrimp populations. Advanced very-high-resolution radiometer (AVHRR) satellite imagery was used to assess water volumes diverted away from the channel of the Colorado River and ultimately the Gulf of California during flooding periods. Analysis of data demonstrated that little freshwater actually reaches the Gulf even during floods because of its diversion into a large dry lake bed basin known as Laguna Salada. Fuller use of the Colorado River throughout its entire course to the sea is possible and could benefit a large cohort of users without catastrophic habitat destruction in delta ecosystems. Reconstruction of a natural earthen berm, as proposed by Ducks Unlimited, would maximize the use of floodwaters for ecosystem benefits. These findings have profound implications for local economic activities dependent on hydrologic resources in the Colorado River Delta and Upper Gulf.

Managing the externalities of declining dry season river flow: A case study from the Ewaso Ngiro North River Basin, Kenya

Upstream‐downstream water conflicts are common phenomenon in most basins. Such conflicts take a different dimension when they occur during dry season with an already low level of river flows. This context aggravates the spatial externalities on downstream communities and water‐dependent ecosystems, causing serious socioeconomic and ecological effects. Utilizing an analytical framework to capture the causes and consequences of the spatial nature of these externalities and relying on both primary and secondary data pertaining to the Upper Ewaso Ngiro North basin in Kenya, this paper (1) shows how these externalities are caused more by upstream land and water use changes than by any climatic and hydrological factors, (2) evaluates the nature and magnitude of their impacts on different downstream community groups, (3) assesses the extent and success of past policy responses and local initiatives, and (4) concludes by indicating the needed approach and interventions for finding a durable solution to the problem of upstream‐downstream water conflicts and externalities.

Long-term annual and seasonal trends in surface salinity of San Francisco Bay

Trends in surface salinity at seven stations in San Francisco Bay were studied. We found that annual surface salinity over the period 1920–1986 at the ocean boundary had slightly increased and at the river boundary, had slightly decreased. None of these trends were statistically different from zero even though upstream water use has nearly doubled. However, statistically significant seasonal trends were found. In most areas, salinity had increased from February through June and decreased at other times. Salinity in the bay is affected primarily by freshwater inflow and oceanic conditions. Seasonal salinity trends at stations near the freshwater boundary are probably largely owing to the operation of upstream water projects, which have redistributed freshwater between the months. At stations near the ocean, seasonal salinity trends appear to be strongly influenced by offshore conditions, including a local rise in sea level and increased upwelling.