Combining fixed and mobile cosmic-ray neutron probes for...
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Combining fixed and mobile cosmic-ray neutron probes for realtime multiscale monitoring of soil moisture Franz TE, School of Natural Resources, University of Nebraska-Lincoln, USA 1. Introduction Approximately 40% of global food production comes from irrigat ed agriculture. With th e increasing demand fo r food even greater pressures will be placed on water resources within these systems. In this work we aimed to characterize th e spatial and temporal patterns of soil moisture at various scales by combining fixed and ro ving cosmic-ray neu tron prob es at three study sites across an East-West precipitation gradien t overtopping the High Plains Aquifer (HPA). Each of th e study sites consisted of co ars e scale mapping of the enti re domain. By using a simplistic data merging technique we are able to produce a statistical daily soil moisture product at a vari ety of key spatial scales in support of irrigation water man agemen t technology: the individual sprinkler (~10 2 m 2 ) for variable rate irrigation, the individual pie slice (~10 3 m 2 ) for variable speed irrigation, and the quarter section (0.64 km 2 ) for uniform rate irrigation. In addition, we are able to provide a daily soil moisture product over the whole study area at a vari ety of key remote sensing and modeling scales 1, 9, and 144 km 2 . These products c an be us ed to support SMAP/SMOS th rough calibration, validation, and value addition by statistical downscaling. 2. Study Site Platte River Basin Cosmic-ray Monitoring Network ( 10 fixed probes) Site Research Objectives 1. Design of cos t eff ec tive, accurate, and pragm atic monitoring techniques in support of variable rat e and variable speed sprinkler irrigation packages. 2. Design of monitoring technique to provide spatial es timat es of top boundary condition (recharge) in support of groundwater flow model at study site. 3. Design of basin wide monitoring of 100’s of center pivots in support of scheduling irrigation timing and depth for uniform rate irrigation. 3 1 2 3. Data Merging Technique Fixed cosmic-ray neutron probe measuring neutron counts every hour Roving cosmic-ray neutron probe measuring neutron counts every minute 1. Convert fi xed neutron counts int o daily averaged soil water content 2. Convert roving neutron count s into spatial soil water content map using geostatistical methods 3. For spe ci fied geometry, per for m linear regression between area average soil water content (rover ) and corresponding (in time) fixe d probe soil water content 4. Use regression relationships, regression coefficients, and time series of fixed probe soil water conte nt to construct a continuous daily spatial product Details of methodology can be found in Franz et al. (2015 GRL) 4. Precision Agriculture Data merging results in support of variable rate irrigation Data merging results in support of variable speed irrigation 5. Small Watershed Monitoring Data merging results in support of Modflow grid 6. Watershed Monitoring Data merging results in support of uniform rate irrigation 9. Acknowledgments This research is supported by the Daugherty W ater for Food Ins titute at the University of Nebraska, Cold Regions Research Engineering Laboratory, USGS 104B, and the UNL Layman Award. We would also like to thank The Nature Conservancy, Paulman Farms, Nebraska Water Balance Alliance, The Western Irrigation Project, and the Platte River Recovery Project for providing access to field sites, on-site support, and ancillary data. We would like to thank Gary Womack and Darin Desilets for support with the rover. For more information about DWFI and the Hydrogeophysics lab group please visit http:/ / tfranz 2.wix.c om/ trenton-franz 7. Summary and Conclusions 1. Combining fixed and roving cosmic-ray neutron probes is a feasible and cost effective strategy to continuously monitor near surface soil water content at a variety of scales. 2. Arbitrary geometry of the method makes it applicable to water resource management in aiding decision making in irrigation. 3. The arbitrary geometry makes the method applicable to matching modeling grids or comparing to remote sensing products. 4. Accuracy of the method (R 2 and p value) is dependent on selected spatiotemporal scale and rover mapping resolution. Daily products at ~50x50 m is feasible. 5. Data mining techniques of neural networks and deep learning will be explored to maximize correlation and flexibility with scaling. 8. Reference Franz, T. E., T . Wang, W . Avery, C. Finkenbin er and L. Brocca (2015). "Combined analys is of soil moisture m easurem ents from roving and fixed cosmic ray neutron probes for multiscale real-time monitoring." Geophysical Research Letters 42.
Transcript of Combining fixed and mobile cosmic-ray neutron probes for...
Combining fixed and mobile cosmic-ray neutron probes for realtime multiscale monitoring of soil moisture
Franz TE, School of Natural Resources, University of Nebraska-Lincoln, USA
1. IntroductionApproximately 40% of global food production comes from irrigatedagriculture. With th e increasing demand fo r food even greater pressures willbe placed on water resourc es within these systems. In this work we aimedto characterize th e spatial and temporal patterns of soil moisture at variousscales by combining fixed and ro ving cosmic-ray neu tron prob es at threestudy sites across an East-West precipitation gradien t overtopping the HighPlains Aquifer (HPA). Each of th e study sites consisted of co ars e scalemapping of the enti re domain. By using a simplistic data merging techniquewe are able to produce a statistical daily soil moisture product at a vari ety ofkey spatial scales in support of irrigation water man agemen t technology: theindividual sprinkler (~102 m2) for variable rate irrigation, the individual pieslice (~103 m2) for variable speed irrigation, and the quarter sec tion (0.64km2) for uniform rate irrigation. In addition, we are able to provide a dailysoil moisture product over the whole study area at a vari ety of key remotesensing and modeling scal es 1, 9, and 144 km2. These products c an be us edto support SMAP/SMOS th rough calibration, validation, and value additionby statistical downscaling.
2. Study Site
Platte River Basin Cosmic-ray Monitoring Network ( 10fixed probes)
SiteResearchObjectives
1. Design of cos t effec tive, accurate, and pragm aticmonitoring techniques in support of variablerate and variable speed sprinkler irrigationpackages.
2. Design of monitoring technique to providespatial es timates of top boundary condition(recharge) in support of groundwater flowmodel at study site.
3. Design of basin wide monito ring of 100’s ofcenter pivots in support of scheduling irrigationtiming and depth for uniform rate irrigation.
3 1 2
3. Data Merging Technique
Fixed cosmic-ray neutron probemeasuring neutron counts everyhour
Roving cosmic-ray neutron probemeasuring neutron counts everyminute
1. Convert fi xed neutron counts int odaily averaged soil water content
2. Convert roving neutron count s intospatial soil water content map usi nggeostatistical methods
3. For speci fied geometry, per formlinear regression between areaaverage soil water content (rover )and corresponding (i n time ) fixedprobe soil water content
4. Use regression relationships,regression coefficients, and timeseries of fixed probe soil watercontent to construct a continuousdaily spatial product
Details of methodology can be found inFranz et al. (2015 GRL)
4. Precision Agriculture
Data merging results in support of variable rate irrigation
Data merging results in support of variable speed irrigation
5. Small Watershed Monitoring
Data merging results in support of Modflow grid
6. Watershed Monitoring
Data merging results in support of uniform rate irrigation
9. AcknowledgmentsThis research is supported bytheDaugherty Water for FoodInstitute atthe Univers ityofNebraska,ColdRegions Research Engineering Laboratory, USGS104B,and theUNLLaymanAward. Wewouldalsoliketothank TheNature Conservancy,Paulman Farms, NebraskaWaterBalanceAlliance, TheWestern IrrigationProject, and thePlatte River Recovery Project for providing access tofields ites ,on-s itesupport, andancillarydata. Wewouldliketothank GaryWomackandDarin Des ilets for support with the rover.Formore information about DWFI andthe Hydrogeophys ics labgroup pleasevis ithttp:/ / tfranz2.wix.com/trenton-franz
7. Summary and Conclusions1. Combining fixed and roving cosmic-ray neutron probes is a
feasible and cost effective strategy to continuously monitornear surface soil water content at a variety of scales.
2. Arbitrary geometry of the method makes it applicable towater resource management in aiding decision making inirrigation.
3. The arbitrary geometry makes the method applicable tomatching modeling grids or comparing to remote sensingproducts.
4. Accuracy of the method (R2 and p value) is dependent onselected spatiotemporal scale and rover mapping resolution.Daily products at ~50x50 m is feasible.
5. Data mining techniques ofneural networks and deep learningwill be explored to maximize correlation and flexibility withscaling.
8. ReferenceFranz, T. E., T. Wang, W. Av ery, C. Finkenbin er and L. Brocca (2015). "Combinedanalys is of soil moisture m easurem ents from roving and fixed cosmic ray neutronprobes for multiscale real-time monitoring." Geophysical Research Letters 42.
