Integrating Multiscale Observations of U.S. Waters (2008) / Chapter Skim
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Pages 22-61
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Sensor Network Configurations Beyond the traditional sensor network, an emerging technology that is becoming increasingly important is the "embedded sensor network" (ESN; e.g., Seders et al., 2007) , also PREPUBLICATION COPY
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. For example, sensor networks may be programmed to switch from low-level hourly or daily sampling to more frequent sampling when one pod or a group of pods senses a potential hydrologic event, such as the start of an algal bloom or a change in stream stage in response to a storm event.
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TABLE 2-1 Embedded Sensor Network (ESN)
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The Need for New Sensor Probe Technologies Fortunately, in concert with development of ESN technologies, sensors themselves are becoming increasingly smaller, more robust, and less expensive. In particular, physical sensors such as those that measure air and water temperature, water pressure, radiation, relative PREPUBLICATION COPY
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The embedded sensor network controls the storage of stormwater runoff in a large retention basin using level data from sensors within the basin and at the combined sewage system outfall, which is several miles away. Before the embedded sensor network was in place, the basin often was ineffective, resulting in CSO events following even relatively small storms.
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. Development of a wide range of field-robust chemical and biological sensors is one of the greatest challenges facing widespread deployment of sensor networks in the hydrologic sciences.
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oxygen PREPUBLICATION COPY
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They point out that one of PREPUBLICATION COPY
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Carbon nanotubes and nanoparticles can be PREPUBLICATION COPY
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One of the reasons for the preferential development in medicine and biochemistry is the ability to commercialize the sensor technologies for a large and potentially lucrative market. The environmental community needs to keep careful track of the biomedical community's sensor developments and to seek out opportunities to expand nanosensor use to samples of environmental interest.
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. Fundamental hydrobiogeochemical questions raised by more traditional sampling approaches can be explored mechanistically by use of these in-situ reactors PREPUBLICATION COPY
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of an Antarctic Dry Valley stream were as fast as indicated by stream chemistry measurements; the fast weathering rates appeared to be at odds with the fact that mineral weathering rates are thought to be slow at low temperature and in the absence of vascular plants. Mica chips were buried in in-situ microcosms in the hyporheic zone of Green Creek, a McMurdo Dry Valley stream for 39 days of the short Antarctic "summer" PREPUBLICATION COPY
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Arsenic in drinking water can pose a serious human health risk; arsenic has been linked to a variety of different types of cancer, to serious skin conditions, and to nervous system PREPUBLICATION COPY
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In addition, a 3-dimensional laser scanner is used to build a model of the tree and shrub canopies to collect data for modeling of solar interception and to produce volumetric biomass measurements. This network of fixed and mobile sensors is providing continuous measurements of microclimate and soil data at a spatiotemporal resolution that PREPUBLICATION COPY
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sensor system is commonly used. And L-band passive microwave instruments shown their value in soil moisture mapping (see section on Spaceborne Sensors)
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. Airborne data collection might also be used to help design terrestrial- or aquatic-based sensor networks or sensor webs.
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Of the potential airborne PREPUBLICATION COPY
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* Fixed Wing - single piston Commercial Aviat Husky 300 lb/135 kg $200 $500 engine utility - new A-1B Homebuilt Zenith 450 lb/200 kg $200 $500 utility - new CH 801 Fixed wing – single Commercial Fairchild/ 1500 lb/680 kg $1,500 to $2,000 $1,000 turboprop engine utility - used Pilatus Porter Fixed wing - twin turboprop Commercial DeHavilland 1500 lb/680 kg $750 $1,500 engines utility - used Twin Otter Helicopter - single turbine Commercial 1000 lb/450 kg 2,000 $1,500 engine utility - used Commercial About $1 million/month UAV - single piston engine Predator 300 lb/135 kg utility - new (~$30,000-40,000/day)
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The flight hour costs posted in the above table cover primarily the direct operating costs of the aircraft. It is assumed that a member or members of the science team are qualified to pilot the fixed wing, single engine, piston aircraft such as the Aviat Husky or the Zenith CH 801.
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Universities often serve as operators of the simpler of these aircraft, but they typically lack sufficient volume of instrument building and community demand for field use of their instruments to justify dedicated aircraft at the more complex and expensive end of the platform spectrum. One comprehensive Category 3 research program, like the NOAA operation, and several University programs that focus upon new instrument technologies utilizing the less complex airborne platforms might serve as an optimum combination to support hydrologic research.
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Spaceborne sensors offer an unparalleled, synoptic view of the landscape, providing a natural template for upscaling and extrapolating traditional hydrobiogeochemical measurements, in-situ sensor network, and airborne measurements. On the other hand, the direct terrestrial or aquatic and airborne measurements can serve to "ground-truth" satellite remotely sensed data and to provide additional data that cannot be remotely sensed, such as information on details of biochemical reactions in soils or microbial community analysis.
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While land-based systems such as ground-penetrating radar offer promise for monitoring deeper soil water content, and airborne L-band passive microwave instruments have proven soil moisture mapping capabilities (Wang et al., 1989; Jackson et al., 1995, 1999, 2002) , innovative sensor design and antenna technologies are required before the success of ground and aircraft systems can be achieved in space.
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Satellite monitoring of water quality is an important research frontier. All of the research areas described above are certain to advance with development of embedded sensor networks, including new sensors, and integration in environmental observatories.
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15 km x 13 km to 1987-present 69 km x 43 km Moderate Resolution Imaging Spectroradiometer (MODIS) / Terra 500 m x 500 m 2/2000-present Moderate Resolution Imaging Spectroradiometer (MODIS)
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Moderate Resolution Imaging Spectroradiometer (MODIS) / Aqua 500 m x 500 m 7/2002-present Gravity Recovery and Climate Experiment (GRACE)
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Hence, a blueprint for a groundwater observing system in a large aquifer system such as the High Plains would include an embedded sensor network of groundwater monitoring wells, in-situ soil moisture sensors, gravimeters, airborne and remotely sensed soil moisture and GRACE data, assimilated into a spatially-distributed hydrological or groundwater model. The observing system would provide aquifer-average and spatial patterns of groundwater recharge, water table variations, and discharge, which would be available in near-real-time to the user community, using cyberinfrastructure technologies.
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The satellite data could serve as pods in the sensor web, triggering intensive sampling in regions where precipitation is actively falling or anticipated, or as regional soil moisture or river heights increase and contaminants are mobilized, or with the spreading of a freshwater or coastal plume. In Southern California for example, where the beach water quality sampling takes a full day, results are often obsolete by their time of release (Jeong et al., 2007)
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Remote sensing of surface water heights, inundation extent, and groundwater storage changes could be integrated into existing surface and groundwater monitoring and modeling activities in South Florida, and coupled to a coastal observing framework. Such an integrated observing system would not only greatly improve inland and coastal water quality monitoring and prediction, but would enhance decision making information streams with important implications for balancing economic development and societal demands for wetland restoration in the Everglades region.
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The research and development activities related to embedded sensor networks, biogeochemical sensor technologies, and at larger scales sensors designed for airborne and space platforms, offer significant opportunities to advance our understanding of critical hydrological and environmental processes through improved observations at different scales. The committee heard a number of presentations from federal agency scientists, academics and private industry.
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And they can only be used if they can be easily discovered, acquired and understood in a timely and convenient manner by those who wish to apply them to practical issues such as flood forecasting, water availability 58 PREPUBLICATION COPY
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-- the more fundamental PREPUBLICATION COPY
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The application of more advanced techniques is a relatively new phenomenon in hydrology. The renewed interest in hydrologic data assimilation has been spurred in part by the increased availability of remote sensing and ground-based observations of hydrologic variables and/or variables (like soil moisture and surface temperature)
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Hence, the embedded computational ability of embedded sensor networks, combined with multi-scale merging with coarser scale observations and data can allow predictions across scales. CYBERINFRASTRUCTURE: MANAGING THE DATA AND DELIVERING THE PRODUCTS Cyberinfrastructure was defined broadly by an NSF Blue Ribbon Panel (2003)
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