Analysis of Effective Efficiency in decision making for irrigation interventions

Multiple stresses are putting great pressure on water resources systems. Population growth, climate change, prosperity, energy production, food crisis, and water governance are among the factors straining water resources. Decision makers from rich to poor countries and from commercial to non-governmental organisations are struggling to devise schemes to adapt to these stressed water conditions. Better efficiency for water resources systems, and particularly irrigation systems, is recommended as one of the most important responses to climate change, unsustainable development, and water shortage. However, using certain efficiencies such as Classical Efficiency caused systems not to perform according to decision makers?? objectives. Effective Efficiency is a robust composite indicator that includes in its formulation both a flow weight, taking into account the leaching fraction, and reuse of return flows. Classical Efficiency is defined as the percentage of the diversion consumed beneficially, such as by crop evapotranspiration. Effective Efficiency, on the other hand, is defined as the ratio of beneficial consumptive use to total consumption, expressed as a percentage. In this paper, a normalised and non-dimensional form of Effective Efficiency is developed and necessary constraints for its successful application are explained. These constraints express water balance, flow weights and their thresholds, water reuse, and total consumptive use. Basic guidelines are proposed for better decision making in determining possible interventions for improving Effective Efficiency. This is done by analysing its domain through analytical and graphical methods. Three real cases are considered, namely, Imperial Irrigation District and Grand Valley irrigation systems in the United States and Nile Valley in upper Egypt. Three-dimensional sensitivity analysis is performed on Effective Efficiency and its variables using the three cases. This leads to an examination of the validity of the analysis and to suggestions for better intervention options. Meanwhile, it is also shown why Classical Efficiency should be used with care.     

Prediction of modified Mercalli intensity from PGA, PGV, moment magnitude, and epicentral distance using several nonlinear statistical algorithms

Despite technological advances in seismic instrumentation, the assessment of the intensity of an earthquake using an observational scale as given, for example, by the modified Mercalli intensity scale is highly useful for practical purposes. In order to link the qualitative numbers extracted from the acceleration record of an earthquake and other instrumental data such as peak ground velocity, epicentral distance, and moment magnitude on the one hand and the modified Mercalli intensity scale on the other, simple statistical regression has been generally employed. In this paper, we will employ three methods of nonlinear regression, namely support vector regression, multilayer perceptrons, and genetic programming in order to find a functional dependence between the instrumental records and the modified Mercalli intensity scale. The proposed methods predict the intensity of an earthquake while dealing with nonlinearity and the noise inherent to the data. The nonlinear regressions with good estimation results have been performed using the ??Did You Feel It??? database of the US Geological Survey and the database of the Center for Engineering Strong Motion Data for the California region.     

Spatial and temporal variability of phytoplankton and environmental factors in a temperate estuary of South America (Atlantic coast,Argentina)

A spatial and temporal study on data collected along the longitudinal gradient of the Principal Channel of Bahía Blanca estuary, Argentina, was carried out during 1992–1993. At nine stations, phytoplankton abundance, chlorophyll a (Chl-a) concentration, inorganic nutrient levels, Secchi disk depth, euphotic depth:mixing depth ratio (Z_eu:Z_m), salinity and temperature were recorded. Phytoplankton abundance, Chl-a concentration and nutrient levels decreased towards the outer zone of the estuary. The inner zone (stations 1 and 2), which was characterized by high turbidity, high nutrient concentrations and high Z_eu:Z_m (>0.16, [critical mixing ratio]), registered the highest phytoplankton abundance and Chl-a concentrations. Temporal variability of data was also noteworthy in this zone. The highest biomass values thus corresponded to June, July, August and the beginning of spring (18 μg Chl-a L⁻¹ and 9×10⁶ cells L⁻¹) concomitantly with a diatom bloom. In the middle zone (stations 3–6), a strong phytoplankton biomass decrease was observed and it coincided with both deep-mixed depths and low Z_eu:Z_m (<0.16). The outer zone (stations 7–9), which was characterized by low phytoplankton biomass values and low nutrient levels all along the year, was the area mostly influenced by waters from the adjacent continental shelf. In view of the above, it can be concluded that the most important primary production in the Bahía Blanca would be produced in the shallow inner zone during winter, being the spatial reach of the phytoplankton biomass principally limited to estuarine waters. Presumably, less than 5% of such biomass may reach the coastal area of the estuary.     

Concentrated flow erosion as a main source of sediments in Galicia,Spain

Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, field observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated flow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the field. Concentrated flow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha^?1 year^?1; (b) generalized rill and ephemeral gully incision in the class of mean values between 2·5 and 6·25 Mg ha^?1 year^?1, this was the most common erosion pattern; and (c) heavy erosion as observed during an extremely wet winter period, between October 2000 and February 2001, with erosion figures that may be about ten orders of magnitude higher, up to 55–60 Mg ha^?1 year^?1. Therefore, low values of soil losses are dominant, but also large values of rill and ephemeral gully erosion occurred during the study period. Copyright © 2009 John Wiley & Sons, Ltd.     

Phytoplankton community variations in tropical coastal area affected where submarine groundwater occurs

The influence of subterranean water discharge on phytoplankton was studied at two localities (Progreso and Dzilam) on the northern coast of the Yucatan Peninsula. Hydrographic and phytoplankton samples were taken monthly between September 1998 and August 1999. High concentration of silicate (>65 μmol L⁻¹) and nitrate (>80 μmol L⁻¹) and low salinity showed the influence of submerged groundwater discharge (SGD) in the area. In Dzilam, hydrological conditions shows low salinity and high concentration of nitrate and silicate favored from the SGD. Meanwhile, high concentrations of ammonium, nitrite, and phosphate at Progreso (>150 000 inhabitants) suggest mixing of SGD and domestic waste waters. Thick-valve pennate diatoms dominated at Dzilam while dinoflagellates dominated in Progreso. Hydrological differences in both study zones suggest that local forcings, and interaction between coastal water masses and SGD plays an important role in hydrological conditions and primary productivity in the coastal zone of Yucatan. The anthropogenic modified SGD in Progreso may affect the nutrient regime and phytoplankton community structure, and may be used as indicator of eutrophication.     

Assessing aquatic macrophyte community change through the integration of palaeolimnological and historical data at Loch Leven,Scotland

Submerged macrophytes have a critical role in lake ecosystems affecting nutrient cycling, sediment stability, and community composition across multiple trophic levels. Consequently temporal changes in the composition of submerged plant populations can have profound ecological implications and key significance from the perspective of lake conservation. By focusing on macro-remains of aquatic macrophytes and extensive historical plant records spanning the last approximately 180 years, this study seeks to evaluate a combined historical-palaeolimnological approach for establishing pre-disturbance macrophytes communities in Loch Leven, Kinross, Scotland and to provide new information regarding temporal trends in its macrophyte vegetation as well as potential drivers of change. Some 81% of the species historically recorded for the core site (east side of St. Serf’s Island) were found as macro-remains. Potamogeton taxa were underrepresented, whereas remains of Elatine hexandra, a small species never recorded historically were found. The core sequence showed good agreement with known floristic changes including an early (pre- ca. 1850) loss of Isoetes lacustris and Lobelia dortmanna and a more recent (post-1910) shift to dominance by Potamogeton and Chara taxa associated with eutrophic conditions. A clear pattern in the relationship between macrofossil principal component analysis (PCA) and loss on ignition suggested a key control of sediment conditions on macrophyte community structure. In particular the major macrophyte community change of the mid-nineteenth century was concurrent with a substantial increase in organic matter, likely linked to a historic lake lowering (early 1830s) which would have beached the former gravel-sand shoreline leading to a much siltier lake littoral. Although recent monitoring data show signs of ecological recovery our study illustrates that Loch Leven remains a long way from its reference state as a lake with characteristic soft-water macrophytes. To achieve a full recovery, sediment properties would need to change in addition to nutrient reduction. Consequently restoration strategies will need to compromise between the desirability of achieving the pre-disturbance state and what is feasible and practicable. Our study shows the clear potential role of a combined palaeolimnological-historical approach for informing lake management decisions.     

Inventory and geometrical changes in small glaciers covering three Northern Patagonian summits using remote sensing and GIS techniques

In the last few decades, a large quantity of research has been performed to elucidate the current behavior of glaciers in southern Chile, especially with respect to the volumetric changes in the outlets of the Northern and Southern Patagonian Icefields (NPI and SPI, respectively). Calculations have shown a generalized thinning and withdrawal, which greatly contributes to the increase in sea level attributed to the ice melt from non-polar glaciers. However, these icefields are surrounded by many small icecaps, which have yet to be studied in detail. A precise estimation of the volume of ice located in these mountain chains could provide new information with respect to this area's exact contribution to the increase in sea level. Thus, this study presents an inventory of relatively small Northern Patagonian glaciers in the surrounding of the three summits: Mount Queulat, and the Macá and Hudson volcanoes. The study used remote sensing techniques in a GIS environment to determine the margins, surface areas, thickness changes and hypsometry for the glaciated zones. Landsat images from different dates were analyzed using standard band ratio and screen delineation techniques. Additionally, digital elevation models from different dates were compared using map algebra, calculating thickness changes. Based on the results, we propose that there are important volumetric changes in the glaciers studied, which could be explained by precipitation trends in a general context, and an influence of the glaciers' sizes in some local response. Therefore, we suggest the exact contribution of the Patagonia to the increase in sea level corresponds to a regional pattern rather than just the behavior of a single ice field.     

<Emphasis Type="SmallCaps">G</Emphasis>reen zero-valent iron nanoparticles for the degradation of amoxicillin

In the last years, it has been proven that zero-valent iron nanoparticles, including those produced using green methods, are efficient remediation agents for a wide range of target contaminants. However, apart from the known advantages of these green nanomaterials, the knowledge of how they act on distinct contaminants is not yet fully understood and requires further investigation. The objectives of this work were to study the degradation of a common antibiotic, amoxicillin, in water and in a sandy soil using green zero-valent iron nanoparticles (gnZVIs) as reductants and as catalysts for the Fenton reaction. It represents the first study of the use of gnZVI, as alternative for the zero-valent iron nanoparticles produced with sodium borohydride, for the degradation of amoxicillin. The results of the performed tests indicate that gnZVIs have the potential to be used in remediation processes. In both chemical tests, the gnZVI was able to degrade up to 100% of amoxicillin in aqueous solutions, using an amoxicillin/gnZVI molar ratio of 1:15 when applied as a reductant, and an amoxicillin/H₂O₂/gnZVI molar ratio of 1:13:1 when applied as a catalyst for the Fenton reaction. The soil tests showed that the required molar ratios for near complete degradation were higher in the reduction test (1:150) than in the gnZVI-catalyzed Fenton reaction (1:1290:73). This is possibly due to parallel reactions with the soil matrix and/or limitations of the reagents to reach the entire soil sample. The degradation efficiencies obtained in these tests were 55 and 97% for the reduction and catalyzed Fenton processes, respectively.