DEFINING THE 'SAVING' IN AGRICULTURE WATER WHEN IRRIGATION TECHNOLOGY IS A CHOICE VARIABLE: THE CASE OF THE KLAMATH BASIN

Increasing demand for water in the environment has increased the cost of irrigation water in agriculture leading to the adoption of water saving irrigation technologies, reducing agricultural return flows. However, when agricultural return flows are a source of environmental supply 'savings' soon disappear because of the reduced agricultural return flowsResource /Energy Economics and Policy,

Optimal Conjunctive Use of Surface and Groundwater with Recharge and Return Flows: Dynamic and Spatial Patterns

This paper derives the efficiency price patterns for a comprehensive spatial and dynamic model of conjunctive water use incorporating conveyance losses, canal return flows, and groundwater recharge. The first-best shadow price of surface water is composed of a charge for water that flows into the farm and differential credits for water that flows to other uses. The shadow prices can be used as the basis of water pricing schemes or for exchange rates to facilitate water trading. We show that farmers near the headworks use irrigation water in the optimal program, and only farmers more distant from the headworks extract groundwater. We also illustrate the possibility of reswitching in the sequence of resource use. It may be efficient for some farms to switch from one source to another and then switch back again, e.g. groundwater to surface water to groundwater.water management, conjunctive use, irrigation, return flows, conveyance loss, consumptive use, sequence of resource use

Three study decades on irrigation performance and salt concentrations and loads in the irrigation return flows of La Violada irrigation district (Spain)

30 Pags., 3 Tabls., 9 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809Irrigation district salt balances identify the main sources and sinks of salts and quantify salt loads in irrigation return flows. Salt balances were performed in La Violada Irrigation District during the 80s (1982–1984), 90s (1995–1998) and 00s (2006–2008) decades. Total Dissolved Solids (TDS) and loads in irrigation return flows were related with changes in irrigation performance and infrastructures during these decades. TDS increased linearly to increases in Irrigation Consumptive Use Coefficient (ICUC) (P 66%, and decreased exponentially for values above and below these thresholds, respectively. Therefore, the key management strategy to reduce salt discharge to downstream areas is to decrease drainage volumes by improving irrigation management.This work was sponsored by the Spanish Ministry of Science and Education project AGL2006-11860/AGR, the European Regional Development Fund (FEDER) and the European Union project INCO CT-2005-015031.Peer reviewe

Microbial Challenges to Extending Usage of Rio Grande River Water

Despite its critical role in agriculture and potable water supply for the region, few studies have evaluated the microbial quality of the Rio Grande River, especially for the parasites Cryptosporidium and Giardia. Cryptosporidium and Giardia cause diarrheal illness and have been responsible for numerous waterborne and foodborne disease outbreaks. Cryptosporidiosis, the disease caused by Cryptosporidium, may be fatal in people with weakened immune systems and there is currently no effective treatment for the disease. During the irrigation season, water is released from upstream reservoirs and the river water is used by El Paso as a potable supply. During the non-irrigation season (October through February), river flows are comprised of agricultural return flows and wastewater treatment plant effluents. Due to recent drought conditions in the region, winter return flows in the El Paso area are largely wastewater effluents. Our monitoring results revealed that winter return flows contain 5 and 100 times higher average levels of Cryptosporidium and Giardia, respectively, than irrigation season river water. Recently, research has been proposed to evaluate the use of winter return flows for potable supply and irrigation. Conventional filtration and disinfection followed by nanofiltration or reverse osmosis have been proposed for treatment of the water to remove total dissolved solids and microorganisms. Besides Cryptosporidium and Giardia, viruses may also be present in wastewater effluents. Therefore, in addition to chemical quality issues, these microbial water quality challenges must be overcome before this underutilized water resource can be put to beneficial use

SALMOD, a Salinity Management Tool for Irrigated Agriculture

This paper presents an irrigation farm management tool, SALMOD (Salinity And Leaching Model for Optimal irrigation Development), that calculates the profit maximizing crop enterprise composition and irrigation management options for farm specific soil type, drainage status and irrigation system composition subject to various regional control measures and expected irrigation water salinities. After stating the water quality problem, and particularly salinisation in Southern Africa, the input data requirements and the results of SALMOD and their usefulness at farm level, are discussed. The impact of various possible regional or policy regulations are then discussed. SALMOD was developed for irrigators in the lower Vaal and Riet Rivers in South Africa. These farmers have been experiencing rapidly fluctuating salinity levels in their irrigation water, resulting in soil salinisation, yield loss and subsequent financial instability. SALMOD calculates the profit maximizing crop choice and distribution over the farm, matching the crop choice with soil type, drainage status and irrigation system, indicating the optimal leaching vs. yield reduction seasonal management options as well as calculate long term management options such as underground drainage installation, a change in irrigation system or the construction of on farm storage dams. Leaching is necessary to maintain an acceptable salt balance in the root-zone of irrigated crops. This however contributes to point and non-point source water pollution externalities if not managed correctly. Results show valuable policy information regarding the interactions between artificial drainage subsidisation, return flow restrictions and on-farm storage.Irrigation, water quality, return flows, salinisation, leaching, non-point source pollution, on-farm storage, SALMOD, linear programming, GAMS, Farm Management, Land Economics/Use,

Can smallholder farmers meet the financial costs of irrigation services? A case study on economic efficiency and social equity in South Africa

Considering water as an economic good consists of, among other requisites, properly assessing the cost incurred by supplying and managing the resource, and the required infrastructure thereof. This paper investigates and assesses the full financial costs of irrigation services in smallholder conditions, and discusses the possible match between farmers' performances and the costs incurred, from a case study in South Africa. The paper first presents the specific conditions and features of smallholder irrigation, with emphasis on South African examples. Several specific issues are identified and discussed, such as the lack of records on infrastructure and initial costs, the multiple purpose and actual uses of certain equipment and infrastructure, the shift in purpose of others over time, the inclusion of certain small, yet indispensable equipment in the calculation, the partial refurbishment works on particular assets, and the lack of a standard basis for calculation under tropical, developing conditions (e.g. on service life, maintenance requirements). Second, after a brief review of current frameworks, concepts and terminology, the paper attempts to evaluate financial costs of irrigation services on a case study in South Africa. The results suggest that the application of existing methodologies proves feasible, provided some adapted data and available information replace the original ones, especially for capital costs. This applies to the discount rate, calculation of the current value, and estimation of the service life of infrastructure and equipment. In particular, several scenarios have been tested in order to estimate a surrogate to the discount rate. The average yield on Negotiable Certificates of Deposit (NCD) is suggested as a surrogate for treasury bills, hence for the discount rate. The case study demonstrates the high costs of irrigation services as compared to the low income derived from irrigation production in smallholder schemes; hence the need for renewed public intervention and subsidization, especially on account of the current context of management transfer, privatization, and liberalization. The case also indicates that under the current production levels and marketing practices, farmers would not be able to achieve the targeted return on assets (ROA) of four percent, as suggested by Government. The paper suggests a shift in underlying policy and societal mindset about water charging system in smallholder irrigation. Cost recovery and water charges should not be considered a further burden or deterring factors for smallholder irrigation, but rather incentives towards increased production and ultimately improved contribution to the country's economy. (Résumé d'auteur

Assessing the Direct Economic Effects of Reallocating Irrigation Water to Alternative Uses: Concepts and an Application

Irrigation water reallocations are playing an increasingly important role in both developed and developing countries. With growing urban and environmental water demands, rising costs for the development of new water supplies, and irrigated agriculture usually including the least economically valuable use of water, transfers of irrigation water to alternative uses are increasing. However, such reallocations are often controversial, and it is often questioned whether the benefits resulting from these transactions are large enough to outweigh the associated costs. This paper reviews the experience with irrigation water transfers, including the involvement of the World Bank. It discusses the problems of assessing the direct economic effects of reallocations, with a focus on the foregone direct benefits in irrigated agriculture. Because foregone direct benefits cannot easily be directly observed, they need to be estimated. However, assessments have shown widely differing estimates -- even when the same methodology was used. The paper reviews the methodologies and model specifications used for estimating foregone direct benefits; illustrates the impact of different model specifications on the magnitude of estimates of foregone direct benefits based on an application in an example case; and draws conclusions with regard to future efforts in assessing reallocation effects, including calculating adequate compensation for farmers. Because estimating the direct benefits of irrigation expansion is methodologically equivalent to estimating foregone direct benefits from reduced irrigation water supplies, the findings have implications for a broader range of water allocation decisions

Hydrological Foundation as a Basis for a Holistic Environmental Flow Assessment of Tropical Highland Rivers in Ethiopia

The sustainable development of water resources includes retaining some amount of the natural flow regime in water bodies to protect and maintain aquatic ecosystem health and the human livelihoods and wellbeing dependent upon them. Although assessment of environmental flows is now occurring globally, limited studies have been carried out in the Ethiopian highlands, especially studies to understand flow-ecological response relationships. This paper establishes a hydrological foundation of Gumara River from an ecological perspective. The data analysis followed three steps: first, determination of the current flow regime flow indices and ecologically relevant flow regime; second, naturalization of the current flow regime looking at how flow regime is changing; and, finally, an initial exploration of flow linkages with ecological processes. Flow data of Gumara River from 1973 to 2018 are used for the analysis. Monthly low flow occurred from December to June; the lowest being in March, with a median flow of 4.0 m(3) s(-1). Monthly high flow occurred from July to November; the highest being in August, with a median flow of 236 m(3) s(-1). 1-Day low flows decreased from 1.55 m(3) s(-1) in 1973 to 0.16 m(3) s(-1) in 2018, and 90-Day (seasonal) low flow decreased from 4.9 m(3) s(-1) in 1973 to 2.04 m(3) s(-1) in 2018. The Mann-Kendall trend test indicated that the decrease in low flow was significant for both durations at alpha = 0.05. A similar trend is indicated for both durations of high flow. The decrease in both low flows and high flows is attributed to the expansion of pump irrigation by 29 km(2) and expansion of plantations, which resulted in an increase of NDVI from 0.25 in 2000 to 0.29 in 2019. In addition, an analysis of environmental flow components revealed that only four "large floods" appeared in the last 46 years; no "large flood" occurred after 1988. Lacking "large floods" which inundate floodplain wetlands has resulted in early disconnection of floodplain wetlands from the river and the lake; which has impacts on breeding and nursery habitat shrinkage for migratory fish species in Lake Tana. On the other hand, the extreme decrease in "low flow" components has impacts on pin smaller pools. These results serve as the hydrological foundation for continued studies in the Gumara catchment, with the eventual goal of quantifying environmental flow requirements.redators, reducing their mobility and ability to access prey concentrate