A nearly optimal upper bound for the self-stabilization time in Herman's algorithm

Self-stabilization algorithms are very important in designing fault-tolerant distributed systems. In this paper we consider Herman's self-stabilization algorithm and study its expected self-stabilization time. McIver and Morgan have conjectured the optimal upper bound being 0.148N 2, where N denotes the number of processors. We present an elementary proof showing a bound of 0.167N2, a sharp improvement compared with the best known bound 0.521N2. Our proof is inspired by McIver and Morgan's approach: we find a nearly optimal closed form of the expected stabilization time for any initial configuration, and apply the Lagrange multipliers method to give an upper bound of it. © 2014 Springer-Verlag

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.A hydrodynamic model for simulating the flow in Basin irrigation system is presented. An explicit McCormack method is used for solving the governing equations. This method doesn't require any special treatment of advancing or receding fronts such as sub-grid technique. The numerical procedure accommodates for three inflow boundary conditions namely line inflow, corner inflow and fan inflow. The results are compared with observed advance and recession times for two level basin irrigation events available in the literature and two field experiments conducted by authors at WALMI, Vadod, Anand, Gujarat, India. A very good comparison of results is observed. The results for various other cases are also presented

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.The Shafurud Irrigation Project is located in the North Western part of Iran by the Caspian Sea. At present, traditional water courses are irrigating about 7,150 ha of paddy fields. Even though there are water shortages during low river runoff and peak growing season, it was decided to extend the area under paddy to about 12,300 ha in net. This is not possible without taking full advantage of the river runoff, and preventing the flow of a large volume of water to the Caspian Sea annually. Therefore, it was foreseen to construct a storage dam on one of the four rivers existing in the area, and three diversion darns on the other rivers. By taking full advantage of the river runoff through the diversion darns and provision of irrigation water during deficiency period from the storage dam, the goal can be achieved. The objective of this paper is to describe the design methodology adopted for the Shafurud primary canal by taking into account the operational performance of the system by using the MODIS hydrodynamic flow model. In the design of new primary canal, it was decided to investigate the effect of manual operation of secondary offtakes and impact of river runoff variation in two alternatives of automatic upstream and self-regulating downstream control systems during deficiency and sufficiency river runoff periods. The results of the simulation show that the unsteady flow phenomena has an important effect on the water delivery and operational efficiency of the system, specially in the case of alternative using an automatic upstream control. It was noticed that management by automatic upstream control is difficult, and during sufficient river runoff relatively more flow should be released from the storage darn as compared with its variant alternative of self-regulating downstream control system but due to topographical condition of the canal alignment with a few modifications it was considered to be a better design option. The idea of taking into account the operational performance of a new irrigation system at the time of design is becoming increasingly important every day, especially when it is realized that many old irrigation schemes do not function properly. One of the main reasons is that water distribution and unsteady flow conditions were hardly considered in their design

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.A field study was conducted at Mashtul Pilot Area MPA (260 feddans' 1 feddan = 4200 m2) situated at north Zagazig to evaluate the performance of the long term constructed subsurface drainage system. The evaluation of grades, alignment and clogging of drain lines can give an indication of the system performance and efficiency. Three drainage units served by the same collector were selected. Four 30 m interval PVC lateral pipes were installed at different depths. The results revealed that, the collector drain slopes were either steep or flat while the overall slope of the collector drain was considered steep for about 45.50% of the sections and flat for the rest. On the other hand, some sections showed an inverse slope which can cause a decrease in the discharge rate. The regularity was classified as good for about 82% of the sections and moderate for the rest. The slope of the lateral drains was correct for 41.7% of those under study (12 lateral drains), steep for 16.60%, and flat for the rest, and the regularity was classified as poor except lateral number 71 which had moderate regularity in the first approach while, in the second approach 41.67% had moderate regularity and poor for the rest. Also the deviation of the drain pipes from the straight line was generally larger than pipe diameter. Consequently, air entrapment and sedimentation resulted. The results also indicated that, the average height of sedimentation inside lateral drains was 12.70 mm (618.30 gm/m drain length) while for collector drains, sediment was in 22.88% of pipe diameter. The average reduction in discharge capacity due to sedimentation for laterals and collectors upstream and downstream parts were 17.17%, 32.80% and 17.60% respectively. Also using Manning, Visser and Wesseling equations leads to different safety factors

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.Washington State University is implementing a Scientific Irrigation Scheduling (SIS) Project that is being funded by the public utility districts through the Northwest Energy Efficiency Alliance (1998 through 2000). Scientific irrigation scheduling is defined as the use of crop evapotranspiration data and soil moisture sensors to accurately determine when and how much to irrigate. The project goal is market transformation. In other words, scientific irrigation scheduling will become a common practice that does not require continual government subsidy to be maintained. A 50% adoption rate will be a key indicator of market transformation in scientific irrigation scheduling. Surveys were conducted during 1997 and 1998 to determine the status of and direction for scientific irrigation scheduling in Washington. According to the survey results, private consultants were contracted to perform irrigation scheduling on nearly 300,000 acres per year. Conservation Districts, county extension, and the National Resource Conservation Service have assisted producers in scheduling irrigation on an additional 15,000 acres per year. Individual Farm enterprises reported scheduling another 55,000 acres of irrigation on their own. The combined effort has resulted in a 17% adoption rate of scientific irrigation scheduling on an acreage basis. Survey results also indicated that potatoes and tree fruit account for more than half of the acreage being scheduled. The main reason producers were willing to pay for irrigation scheduling is to insure the quality of high-value crops. Energy savings became important when water needed to be lifted a considerable distance; however, water conservation, high yield, fertilizer savings, and non-point pollution reduction were considered secondary benefits. Center-pivots were the most likely irrigation systems to be scheduled and a considerable proportion of drip and solid set sprinklers were scheduled, but a very small proportion of furrow systems and set-move sprinklers were scheduled. Of the producers who irrigated farms smaller than 1,000 acres, 75% of the survey respondents have personal computers and 50% have modems but less than 5% are using their computers to schedule irrigation. Since computers and communication technology are available "on-farm," Washington Irrigation Scheduling Expert (WlSE) has been developed as a web-linked and user-friendly software tool that brings together all the pieces needed to implement irrigation scheduling. WISE, soil moisture sensors and other tools will be promoted via traditional demonstration and educational methods but with a different emphasis. Instead of offering irrigators a free service, cooperators will be encouraged to produce their own irrigation schedules from the onset of their involvement with the SIS project and agricultural supply companies will be encouraged to add irrigation scheduling to their services. The goal of this paper and presentation is to document the status, tools, and progress of market transformation in Washington's SIS Project

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.Pakistan owns the large contiguous canal network for irrigating the Indus plains encompassing an area of 16 million ha. The government has now embarked upon reforms to restructure the institutional set-up of irrigation and drainage. The major thrust of these reforms is to transfer the management of secondary and tertiary irrigation and drainage systems to the Farmers' Organizations (FOs), and also involve farmers in the decision making process at the primary level of the system. Important is that the farmers themselves have to appreciate the value of the change, take the initiative to interact with the government, and begin to play a significant role in the participatory management mode. Unless the grass-root level farmers participate in the proposed FOs, there is less likelihood for the social and financial viability of the reforms. The experience to date with the farmers' institutions in Pakistan shows that there has been limited success in establishing functional farmers organizations even at the tertiary level of the irrigation system. A number of professionals are skeptical about the successful establishment and functioning of the proposed FOs as a large proportion of water users are socially vulnerable, politically unorganized and economically weak. Substantially skewed distribution of productive assets necessitates concerted efforts in social organization to ensure that the majority of water users are free to participate. Thus, best practices of organizational methodologies need to be followed to ensure that the reforms are implemented successfully. The International Irrigation Management Institute (IIMI) has been involved in pilot projects for organizing farmers for Distributary management, which proved successful in organizing farmers. These organizations are now anxiously waiting for the government's response to transfer the management responsibilities to FOs. This paper synthesizes the results of the pilot efforts and suggests guidelines for organizing fanners at secondary levels of the canal system and upscaling these organizations to entire river basins in Pakistan

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.The introduction of canal irrigation in the semi-arid regions of the Haryana State of India underlain with saline ground water in early sixties led to the rise in water levels at an annual rate of 0.3 to 1.0 m and secondary salinization adversely affecting crop production. To develop feasible technologies for the reclamation of such areas, a pilot study on sub-surface tile drainage systems was undertaken in an area at the Haryana Agricultural University Farm having shallow water levels and high salinity. The drains with three spacings (24, 48, 72 m) were placed at a depth of 2.5 m. The water levels, drainage rates and soil salinity data from the study area growing vegetable crops (eggplant, tomato and potato) were used to calibrate the Field Agricultural Irrigation and Drainage Simulation (FAIDS) model for the period 1985-1989 and validate it for the period 1989-93. A number of simulations were also carried out to finalize optimum drain configuration (spacing x depth) under existing agrohydrological conditions. The drain configurations of 75 m x 2 m (1st option) and 100 m x 2.5 m (2nd option) performed equally well based on salinity in the root zone and crop performance. In both the options, relative evapotranspiration (ETa/ETp) of 0.81 was attained during the third year of operation of the drainage system under normal rainfall conditions. The occurrence of a maximum one-day rainfall event (1 in 10 years) during the fifth year resulted in the failure of one out of three crops in both the options in that year indicating the necessity of integration of a surface drainage system with the subsurface drainage under abnormal rainfall events. The existing inland basin drainage conditions did not permit the disposal of drainage effluent. The reuse system was therefore, integrated with the drainage system. A model RESBAL was coupled with the calibrated and validated model FAIDS and run for eight years to optimally design a series of connected reservoirs for the disposal of drainage effluent from an area provided with a subsurface drainage system. The possibility of the reuse of the disposed water for irrigation, aqua culture and salt harvesting was also studied comprehensively in order to maintain proper salt balance in the root zone. On the basis of this study, subsurface drainage systems coupled with surface drainage systems are being extended in Haryana to over 2000 ha of the farmers' land severely affected with waterlogging and soil salinity using a tile-laying trenching machine

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.Climate potential in respect to onset, magnitude and risk associated with rainfall for crop production in the Nilwala basin, Southern Sri Lanka was assessed using the daily rainfall of 12 stations scattered in different locations for more than 35 consecutive years (1950-1995). The program CROPWAT was used to assess the irrigation need. It was revealed that rainfall of the basin increases from south to north with increasing elevation and altitude. Within a 70-km distance in the south north gradient, rainfall elevates from 1656 mm at Kekanadura to 4216 mm at Kudawa. The net irrigation requirement of Yala rice in different locations varied from 1012 mm to 1246 mm. It was established that the irrigation need in the Nilwala upper catchment is below 40 % of the total water requirement, but in downstream areas it constitutes above 70% of the total water demand. Therefore both the Yala and Maha seasons in Nilwala downstream areas appeared to be unsuitable for rice cultivation without supplementary irrigation. From April 10th onward until May 20th is the best period for establishment of perennial crops at upper catchment areas. Optimum dates for crop establishment at the mid and lower part of the catchment falls on the 14th meteorological week. It is important to note that delaying crop establishment in Yala by 2 or 3 weeks from the optimum date would result in a considerable increase of irrigation need even in the upper catchment areas; it is not advisable to delay the establishment of Maha rice until October when rice varieties off our month duration are cultivated

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.Non-profit cooperative associations of irrigators--known as Mutual Companies--divert, transport, and manage irrigation water across the arid landscapes of the Western United States. These local organizations empower people to provide themselves with agricultural water under control. This paper describes general attributes of mutual companies and reports that 18 mutual companies operating canals and reservoirs in the Poudre River Valley of Northern Colorado have evolved organized patterns of water use, exchange, and re-use that contribute importantly to water resource productivity, distributional justice, and environmental sustainability. Daily water re-use ratios average 1.9:1 over a 24 year period (1970-1994) and sometimes rise as high as 3.3:1 in a calendar year. This level of water re-use is made possible by the 18 mutual companies and the arrangements that they have made among themselves and other water users over the last century. By studying the attributes and capabilities of mutual companies, we can distill lessons regarding how human beings can better organize themselves to manage water

Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.The loss of land for the production of agricultural crops due to salinity is a major problem worldwide. The means to deal with saline soils by the development of salt-tolerant crops, by leaching, or by using desalinized water are not feasible for many developing areas of the world. VA mycorrhizae (VAM) are known to alleviate salt stress on plants, but a practical method to establish them has not been developed. Preinoculation of lettuce or onion plants with mixtures of VAM fungi cultured from saline or nonsaline soils before transplant into sodic soils was shown to be an effective means of increasing plant tolerance to salt toxicity. This method could be practical for farmers needing to grow crops on saline soils