The impacts of management reform on irrigation water use efficiency in the Guanzhong plain, China

This paper examines the efficiency of the 1998 irrigation management reform in the Guanzhong Plain, Shaanxi, China, at farm and canal level. Stochastic frontier analysis is applied to estimate irrigation water use efficiency, based on panel data for 800 farmers, spread over 80 irrigation canals, for the period 1999–2005. Analysis of determinants of water use efficiency shows that at farm level, water price and disclosure are important factors. Compared to the base case of unreformed, management reform has a positive impact with water user association having the largest effect, followed by joint-stock co-operative and private company. The canal model is in line with the farm level model, although estimates are less significant.

Effects of arsenic-contaminated irrigation water on growth, yield, and nutrient concentration in rice

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry-season) rice (Oryza sativa) and their residual effects on the following Aman (wet-season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L-1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L-1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L-1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 μg g-1 and its concentration in rice straw varied from 2.4 to 9.6 μg g-1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus. Copyright © Taylor & Francis Group, LLC.

Adoption of farm-based irrigation water-saving techniques in the Guanzhong Plain, China

This article analyses adoption of farm-based irrigation water saving techniques, based on a cross-sectional data set of 357 farmers in the Guanzhong Plain, China. Approximately 83% of the farmers use at least one farm-based water-saving technique. However, the traditional, inefficient techniques border and furrow irrigation are still prevalent whereas the use of advanced, more efficient techniques is still rather rare. We develop and estimate an adoption model consisting of two stages: awareness of water scarcity and intensity of adoption. We find that awareness of water scarcity and financial status enhance adoption of more advanced techniques whereas access to better community-based irrigation infrastructure discourages it. We furthermore find both community-based irrigation infrastructure and farm-based irrigation water-saving techniques have mitigating effects on production risk. From the results it follows that adoption can be stimulated via financial support and via extension aimed at enhancing awareness of water scarcity.

Reservoirs for irrigation, water-power and domestic water- supply ; with an account of various types of dams and the...

UANL

More than irrigation - The Balinese Subak system as a unique form of cooperative water resource management in Indonesia

For over 1,000 years, the Balinese have developed a unique system of democratic and sustainable water irrigation. It has shaped the cultural landscapes of Bali and enables local communities to manage the ecology of terraced rice fields at the scale of whole watersheds. The Subak system has made the Balinese the most productive rice growers in Indonesia and ensures a high level of food sovereignty for a dense population on the volcanic island. The Subak system provides a vibrant example of a diverse, ecologically sustainable, economically productive and democratic water management system that is also characterized by its nonreliance on fossil fuel derivatives or heavy machinery. In 2012, UNESCO has recognized five rice terraces and their water temples as World Heritage site and supports its conservation and protection. However, the fragile Subak system is threatened for its complexity and interconnectedness by new agricultural practices and increasing tourism on the island.

Near-surface distributions of soil water and water repellency under three effluent irrigation schemes in a blue gum (Eucalyptus globulus) plantation

Water repellent soils are difficult to irrigate and susceptible to preferential flow, which enhances the potential for accelerated leaching to groundwater of hazardous substances. Over 5 Mha of Australian soil is water repellent, while treated municipal sewage is increasingly used for irrigation. Only if a critical water content is exceeded will repellent soils become wettable. To avoid excessive loss of water from the root zone via preferential flow paths, irrigation schemes should therefore aim to keep the soil wet enough to maintain soil wettability. Our objective was to monitor the near-surface water content and water repellency in a blue gum (Eucalyptus globulus) plantation irrigated with treated sewage. The plantation's sandy soil surface was strongly water repellent when dry. For 4 months, three rows of 15 blue gum trees each received no irrigation, three other rows received 50% of the estimated potential water use minus rainfall, and three more rows received 100%. During this period, 162 soil samples were obtained in three sampling rounds, and their water content (% dry mass) and degree of water repellency determined. Both high and low irrigation effectively wetted up the soil and eliminated water repellency after 2 (high) or 4 (low) months. A single-peaked distribution of water contents was observed in the soil samples, but the water repellency distribution was dichotomous, with 44% extremely water-repellent and 36% wettable. This is consistent with a threshold water content at which a soil sample changes from water repellent to wettable, with spatial variability of this threshold creating a much wider transition zone at the field scale. We characterized this transition zone by expressing the fraction of wettable samples as a function of water content, and demonstrated a way to estimate from this the wettable portion of a field from a number of water content measurements. To keep the plantation soil wettable, the water content must be maintained at a level at which a significant downward flux is likely, with the associated enhanced leaching. At water contents with negligible downward flux, the field is water repellent, and leaching through preferential flow paths is likely. Careful management is needed to resolve these conflicting requirements.

The impacts of recycled water on Great Western vineyard soils

Recycled water has facilitated expansion of viticulture in Great Western, Victoria. The recycled water is of medium salinity, and has high concentrations of nutrients and sodium. Irrigation has resulted in increased topsoil EC, pH, and ESP. Laboratory studies identified spatially heterogeneous soils which present a risk of groundwater and offsite contamination.

Measurement systems of soil water matric potential and evaluation of soil moisture under different irrigation depths

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Digital image analysis of root distribution towards improved irrigation water and soil management: Grapevine and date palm study cases

It is presented two study cases about the approach in root analysis at field and laboratory conditions based on digital image analysis. Grapevine (Vitis vinifera L.) and date palm (Phoenix dactylifera L.) root systems were analyzed by both the monolith and trench wall method aided by digital image analysis. Correlation between root parameters and their fractional distribution over the soil profile were obtained, as well as the root diameter estimation. Results have shown the feasibility of digital image analysis for evaluation of root distribution.

Effects of irrigation on water use and water use efficiency in two fast growing Eucalyptus plantations

Eucalyptus plantations occupy almost 20 million ha worldwide and exceed 3.7 million ha in Brazil alone. Improved genetics and silviculture have led to as much as a three-fold increase in productivity in Eucalyptus plantations in Brazil and the large land area occupied by these highly productive ecosystems raises concern over their effect on local water supplies. As part of the Brazil Potential Productivity Project, we measured water use of Eucalyptus grandis x urophylla clones in rainfed and irrigated stands in two plantations differing in productivity. The Aracruz (lower productivity) site is located in the state of Espirito Santo and the Veracel (higher productivity) site in Bahia state. At each plantation, we measured stand water use using homemade sap flow sensors and a calibration curve using the clones and probes we utilized in the study. We also quantified changes in growth, leaf area and water use efficiency (the amount of wood produced per unit of water transpired). Measurements were conducted for 1 year during 2005 at Aracruz and from August through December 2005 at Veracel. Transpiration at both sites was high compared to other studies but annual estimates at Aracruz for the rainfed treatment compared well with a process model calibrated for the Aracruz site (within 10%). Annual water use at Aracruz was 1394 mm in rainfed treatments versus 1779 mm in irrigated treatments and accounted for approximately 67% and 58% of annual precipitation and irrigation inputs respectively. Increased water use in the irrigated stands at Aracruz was associated with higher sapwood area, leaf area index and transpiration per unit leaf area but there was no difference in the response of canopy conductance with air saturation deficit between treatments. Water use efficiency at the Aracruz site was also not influenced by irrigation and was similar to the rainfed treatment. During the period of overlapping measurements, the response to irrigation treatments at the more productive Veracel site was similar to Aracruz. Stand water use at the Veracel site totaled 975 mm and 1102 mm in rainfed and irrigated treatments during the 5-month measurement period respectively. Irrigated stands at Veracel also had higher leaf area with no difference in the response of canopy conductance with air saturation deficit between treatments. Water use efficiency was also unaffected by irrigation at Veracel. Results from this and other studies suggest that improved resource availability does not negatively impact water use efficiency but increased productivity of these plantations is associated with higher water use and should be given consideration during plantation management decision making processes aimed at increasing productivity. Published by Elsevier B.V.