Sensitivity analysis of optimal operation of irrigation supply systems with water quality considerations

Abstract. A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l −1 . The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m 3 h −1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m 3 h −1 reduces the total cost by about 8%

New report charts course for future of geosciences

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95550/1/eost14543.pd

Membranes by the Numbers

Many of the most important processes in cells take place on and across membranes. With the rise of an impressive array of powerful quantitative methods for characterizing these membranes, it is an opportune time to reflect on the structure and function of membranes from the point of view of biological numeracy. To that end, in this article, I review the quantitative parameters that characterize the mechanical, electrical and transport properties of membranes and carry out a number of corresponding order of magnitude estimates that help us understand the values of those parameters.Comment: 27 pages, 12 figure

Defining multiple inhabitations of a cave environment using interdisciplinary archaeometry: the ‘Christmas Cave’ of the Wadi en-Nar/Nahal Qidron, west of the Dead Sea

The present study reports a series of interdisciplinary archaeometrical analyses of objects found in the Christmas Cave, which was discovered by John Allegro and his team in 1960 on the West Bank of the Dead Sea and assumed to be inhabited only in the Chalcolithic era and by Jewish refugees of the second century CE, at the end of the Bar Kokhba Revolt. Like many other Judaean desert caves, there was an abundance of organic material, especially textiles, surviving in the dry environment. In the absence of clear stratigraphy and even a proper publication of the finds, the present study shows how archaeometry can provide important insights. We analysed food crusts on ceramics by gas chromatography with mass spectrometric detection (GC–MS), made petrographic descriptions to estimated provenance of the ceramics, produced new radiocarbon dates from organic material and thermoluminescence (TL) dates from the pottery. It appears from the data that the Christmas Cave has been briefly inhabited or visited intermittently over a very long time, starting ca. 4000 BCE (the Chalcolithic period), and extending all the way to the Medieval period, even though there is also a concentration of dates near the period of the Bar Kokhba Revolt (132–136 CE). We argue, through a detailed analysis of the radiometric and TL-datings and by the artefactual evidence, that there was likely another refuge episode connected with the First Jewish Revolt during which people fled to this cave. However, we see no material connection to Qumran and nearby caves. Overall, our study demonstrates the importance of archaeometric studies in cave environments where stratigraphy is veritably absent