Impacts of Reduced Water Availability on Lower Murray Irrigation, Australia

This article evaluates irrigated agriculture sector response and resultant economic impacts of climate change for a part of the Murray Darling Basin in Australia. A water balance model is used to predict reduced basin inflows for mild, moderate and severe climate change scenarios involving 10, 20, 40 Celcius warming, and predict 13%, 38% and 63% reduced inflows. Impact on irrigated agricultural production and profitability are estimated with a mathematical programming model using a two-stage approach that simultaneously estimates short and long-run adjustments. The model accounts for a range of adaptive responses including: deficit irrigation, temporarily fallowing some areas, and permanently reducing irrigated area and changing the mix of crops. The results suggest that relatively low cost adaptation strategies are available for moderate reduction in water availability and thus costs of such reduction are likely to be relatively small. In more severe climate change scenarios greater costs are estimated, adaptations predicted include a reduction in total area irrigated, investments in efficient irrigation, and a shift away from perennial to annual crops as the latter can be managed more profitably when water allocations in some years are very low.water availability, irrigation, Murray Darling Basin, climate change

Economic assessment of acquiring water for environmental flows in the Murray Basin

This article is an economic analysis of reallocating River Murray Basin water from agriculture to the environment with and without the possibility of interregional water trade. Acquiring environmental flows as an equal percentage of water allocations from all irrigation regions in the Basin is estimated to reduce returns to irrigation. When the same volume of water is taken from selected low-value regions only, the net revenue reduction is less. In all scenarios considered, net revenue gains from freeing trade are estimated to outweigh the negative revenue effects of reallocating water for environmental flows. The model accounts for how stochastic weather affects market water demand, supply and requirements for environmental flows. Net irrigation revenue is estimated to be $75 million less than the baseline level for a scenario involving reallocating a constant volume of water for the environment in both wet and dry years. For a more realistic scenario involving more water for the environment in wet and less in dry years, estimated net revenue loss is reduced by 48 per cent to$39 million. Finally, the external salinity-related costs of water trading are estimated at around $1 million per annum, a quite modest amount compared to the direct irrigation benefits of trade.Resource /Energy Economics and Policy,

Fishery productivity and its contribution to overall agricultural production in the Lower Mekong River Basin

The Mekong River and its ecosystems have one of the most diverse and abundant fisheries in the world. The fisheries are a major factor in the well-being and livelihoods of the nearly 70 million people especially in the lower Mekong Basin who derive their livelihood from fishery and also depend on fish and other aquatic animals for nutrition and food security. Fishery production and value have been the subject of many studies and some data are available from national and international statistical databases. None of these, however, offer a reliable, consistent set of data on the spatial and temporal trends at a similar level of resolution across the basin. Because of the shortcomings in the data, there are major uncertainties in estimates of fishery production and its value in the four countries of the lower Mekong Basin: Cambodia, Lao PDR, Thailand and Viet Nam. Catch surveys tend to underestimate the production, while consumption-based estimates are regarded as more reliable indicators. We combined official statistics with several consumption-based estimates to examine the spatial and temporal trends in production and value of capture fish and aquaculture. The highest estimates of production range from 42 kg/capita/year in the Lao PDR to 65 kg/capita/year in Cambodia, the latter figure being comparable to consumption in Japan. Production is dominated by capture fisheries in Cambodia (where it is concentrated around the Tonle Sap and the Mekong River), Laos and Thailand. In Viet Nam, aquaculture dominates production and is concentrated around the main rivers in the delta and along the coastal strip. While there are uncertainties in the data, it appears that production until 2005 from capture fisheries has not increased significantly in all the four lower Mekong countries. In aquaculture, there has been a large increase in production in the Mekong Delta region of Viet Nam since about 2000. The highest estimates of value, using consumption-based estimates of production, mainly from capture fisheries, give an annual value of about US$3 billion. Other estimates place the overall value somewhat lower. The value is probably not changing greatly with time. Aquaculture in Viet Nam is rapidly increasing in value, matching the increase in production, and in 2005 was worth over US$1 billion. The contribution of the fishing sector to overall agricultural production (crops, livestock and fish) is small in the Lao PDR and Thailand, but larger in Cambodia and growing in Viet Nam. The demand for fish products will rise in the future, partly as a result of increasing population in the region and partly as a result of increasing incomes. Moreover, there may also be a continuing rise in the export of fish products. The lower Mekong fisheries face threats to production from changed water availability and quality, dams and other barriers affecting fish migration and productivity, and overfishing. If the increased demand is to be met, these threats must be managed so that production, especially of wild capture fish, does not decline. The increasing demand appears unlikely to be met through an increase in production of capture fisheries. The current rapid growth of aquaculture, if it can be maintained, does appear capable of meeting the demand. There are neither quantitative estimates of the limits to growth of this industry, however, nor whether it will pose risks for the capture fisheries since aquaculture needs huge quantities of fish fry as feed. Rice-fish farming may also contribute to increased fish production, but again the impact appears not to have been quantifie

Removing Barriers to Facilitate Efficient Water Markets in the Murray Darling Basin – A Case Study from Australia

Water markets have been seen as an effective way of addressing water scarcity and allocation issues. In this paper we discuss the role and characteristics of water markets in facilitating efficient water allocation. Administrative, regulatory and/or political barriers to effective functioning of water markets are reviewed with a focus on southern Murray-Darling Basin in Australia. A mathematical model is developed to estimate the costs of existing restrictions and the benefits from potential changes in the water markets (eg. removing barriers in temporary water market). The modelling results reveal that when expanding trade from intraregional only to interregional trade, mean annual net returns increased from $2,502 million to$2,590 million (i.e. an increase of $88 million). When the current volume restrictions, exchange rates, and trading charges are in place, mean annual net returns reduced from$2,590 million to $2,573 million (i.e. a reduction of$17 million). The exclusion of any state from the interstate water trading market imposes significant costs. If South Australia, New South Wales or Victoria withdraws from the market, it reduces net returns by $27 million,$31 million and $63 million, respectively, from water trading. In conclusion, the policy implications on strategies to removing market barriers are outlined to facilitate efficient and effective water trading.market barrier, opportunity cost, temporary water market, efficient water market, Australia

Metals Removed by Outflows from Milky Way Dwarf Spheroidal Galaxies

The stars in the dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are significantly more metal-poor than would be expected from a closed box model of chemical evolution. Gas outflows likely carried away most of the metals produced by the dSphs. Based on previous Keck/DEIMOS observations and models, we calculate the mass in Mg, Si, Ca, and Fe expelled from each of eight dSphs. Essentially, these masses are the differences between the observed amount of metals present in the dSphs' stars today and the inferred amount of metals produced by supernovae. We conclude that the dSphs lost 96% to >99% of the metals their stars manufactured. We apply the observed mass function of Milky Way dSphs to the ejected mass function to determine that a single large dSph, like Fornax, lost more metals over 10 Gyr than all smaller dSphs combined. Therefore, small galaxies like dSphs are not significant contributors to the metal content of the intergalactic medium. Finally, we compare our ejected mass function to previous X-ray measurements of the metal content of the winds from the post-starburst dwarf irregular galaxy NGC 1569. Remarkably, the most recent starburst in that galaxy falls exactly on the ejected mass-stellar mass relation defined by the Milky Way dSphs.Comment: 5 pages, 2 figures, accepted to ApJ

Chemical Evolution in Hierarchical Models of Cosmic Structure II: The Formation of the Milky Way Stellar Halo and the Distribution of the Oldest Stars

This paper presents theoretical star formation and chemical enrichment histories for the stellar halo of the Milky Way based on new chemodynamical modeling. The goal of this study is to assess the extent to which metal-poor stars in the halo reflect the star formation conditions that occurred in halo progenitor galaxies at high redshift, before and during the epoch of reionization. Simple prescriptions that translate dark-matter halo mass into baryonic gas budgets and star formation histories yield models that resemble the observed Milky Way halo in its total stellar mass, metallicity distribution, and the luminosity function and chemical enrichment of dwarf satellite galaxies. These model halos in turn allow an exploration of how the populations of interest for probing the epoch of reionization are distributed in physical and phase space, and of how they are related to lower-redshift populations of the same metallicity. The fraction of stars dating from before a particular time or redshift depends strongly on radius within the galaxy, reflecting the "inside-out" growth of cold-dark-matter halos, and on metallicity, reflecting the general trend toward higher metallicity at later times. These results suggest that efforts to discover stars from z > 6 - 10 should select for stars with [Fe/H] <~ -3 and favor stars on more tightly bound orbits in the stellar halo, where the majority are from z > 10 and 15 - 40% are from z > 15. The oldest, most metal-poor stars - those most likely to reveal the chemical abundances of the first stars - are most common in the very center of the Galaxy's halo: they are in the bulge, but not of the bulge. These models have several implications for the larger project of constraining the properties of the first stars and galaxies using data from the local Universe.Comment: Submitted to ApJ, 22 pages emulateapj, 15 color figure

Multi-Element Abundance Measurements from Medium-Resolution Spectra. IV. Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies

We derive the star formation histories of eight dwarf spheroidal (dSph) Milky Way satellite galaxies from their alpha element abundance patterns. Nearly 3000 stars from our previously published catalog (Paper II) comprise our data set. The average [alpha/Fe] ratios for all dSphs follow roughly the same path with increasing [Fe/H]. We do not observe the predicted knees in the [alpha/Fe] vs. [Fe/H] diagram, corresponding to the metallicity at which Type Ia supernovae begin to explode. Instead, we find that Type Ia supernova ejecta contribute to the abundances of all but the most metal-poor ([Fe/H] < -2.5) stars. We have also developed a chemical evolution model that tracks the star formation rate, Types II and Ia supernova explosions, and supernova feedback. Without metal enhancement in the supernova blowout, massive amounts of gas loss define the history of all dSphs except Fornax, the most luminous in our sample. All six of the best-fit model parameters correlate with dSph luminosity but not with velocity dispersion, half-light radius, or Galactocentric distance.Comment: 28 pages, 14 figures; accepted for publication in ApJ; very minor editorial corrections in v

Local Group Dwarf Spheroidals: Correlated Deviations from the Baryonic Tully-Fisher Relation

Local Group dwarf spheroidal satellite galaxies are the faintest extragalactic stellar systems known. We examine recent data for these objects in the plane of the Baryonic Tully-Fisher Relation (BTFR). While some dwarf spheroidals adhere to the BTFR, others deviate substantially. We examine the residuals from the BTFR and find that they are not random. The residuals correlate with luminosity, size, metallicity, ellipticity, and susceptibility of the dwarfs to tidal disruption in the sense that fainter, more elliptical, and tidally more susceptible dwarfs deviate farther from the BTFR. These correlations disfavor stochastic processes and suggest a role for tidal effects. We identify a test to distinguish between the {\Lambda}CDM and MOND based on the orbits of the dwarf satellites of the Milky Way and how stars are lost from them.Comment: 16 pages, 7 figures. Submitted to ApJ. Revised in response to referee repor

Near-Infrared Imaging Polarimetry of the Serpens Cloud Core: Magnetic Field Structure, Outflows, and Inflows in A Cluster Forming Clump

We made deep NIR imaging polarimetry toward the Serpens cloud core. The polarization vector maps enable us to newly detect 24 small IR reflection nebulae with YSOs. Polarization measurements of NIR point sources indicate an hourglass-shaped magnetic field, of which symmetry axis is nearly perpendicular to the elongation of the C18O (J=1-0) or submillimeter continuum emission. The bright part of C18O (J=1-0), submillimeter continuum cores as well as many class 0/I objects are located just toward the constriction region of the hourglass-shaped magnetic field. Applying the CF method, the magnetic field strength was estimated to be ~100 muG, suggesting that the ambient region of the Serpens cloud core is moderately magnetically supercritical. These suggest that the Serpens cloud core first contracted along the magnetic field to be an elongated cloud, which is perpendicular to the magnetic field, and that then the central part contracted cross the magnetic field due to the high density in the central region of the cloud core, where star formation is actively continuing. Comparison of this magnetic field with the previous observations of molecular gas and large-scale outflows suggests a possibility that the cloud dynamics is controlled by the magnetic field, protostellar outflows and gravitational inflows. This appears to be in good agreement with the outflow-driven turbulence model and implies the importance of the magnetic field to continuous star formation in the center region of the cluster forming region.Comment: 36 pages, 11 figures, 2 tables, accepted for publication in the Astrophysical Journa

The water-food-energy nexus in Pakistan: A biophysical and socio-economic challenge

We draw on previous work examining historical trends, likely future water use and food availability in Pakistan and extend the analysis to consider interactions with hydropower generation and the energy demand in food production due to pumping of groundwater for irrigation. Business-as-usual scenarios suggest growing demands for groundwater and energy use for food production as population grows rapidly. However, groundwater use is already unsustainable in many areas, and energy supply is failing to keep up with demand. Quantifying material linkages between water, food and energy provides a means to explore biophysical constraints. Characterising institutional constraints is equally important, as they can be significant barriers to effective stewardship of water, energy and food resources. The experience in Pakistan reinforces this finding, and we discuss the implications for hydrologists