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Boise, ID, United States

Tinkham W.T.,University of Idaho | Smith A.M.S.,University of Idaho | Marshall H.-P.,Boise State University | Link T.E.,University of Idaho | And 2 more authors.
Remote Sensing of Environment | Year: 2014

There is increasing need to characterize the distribution of snow in complex terrain using remote sensing approaches, especially in isolated mountainous regions that are often water-limited, the principal source of terrestrial freshwater, and sensitive to climatic shifts and variations. We apply intensive topographic surveys, multi-temporal LiDAR, and Random Forest modeling to quantify snow volume and characterize associated errors across seven land cover types in a semi-arid mountainous catchment at a 1 and 4. m spatial resolution. The LiDAR-based estimates of both snow-off surface topology and snow depths were validated against ground-based measurements across the catchment. LiDAR-derived snow depths estimates were most accurate in areas of low lying vegetation such as meadow and shrub vegetation (RMSE. = 0.14. m) as compared to areas consisting of tree cover (RMSE. = 0.20-0.35. m). The highest errors were found along the edge of conifer forests (RMSE. = 0.35. m), however a second conifer transect outside the catchment had much lower errors (RMSE. = 0.21. m). This difference is attributed to the wind exposure of the first site that led to highly variable snow depths at short spatial distances. The Random Forest modeled errors deviated from the field measured errors with a RMSE of 0.09-0.34. m across the different cover types. The modeling was used to calculate a theoretical lower and upper bound of catchment snow volume error of 21-30%. Results show that snow drifts, which are important for maintaining spring and summer stream flows and establishing and sustaining water-limited plant species, contained 30. ±. 5-6% of the snow volume while only occupying 10% of the catchment area similar to findings by prior physically-based modeling approaches. This study demonstrates the potential utility of combining multi-temporal LiDAR with Random Forest modeling to quantify the distribution of snow depth with a reasonable degree of accuracy. © 2013 Elsevier Inc.

Li R.,Inner Mongolia Agricultural University | Shi H.,Inner Mongolia Agricultural University | Akae T.,Okayama University | Zhang X.,General Administration of Inner Mongolia Hetao Irrigation District | Flerchinger G.N.,Northwest Watershed Research Center
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010

In accordance with the prevention of soil salination and water-saving irrigation in autumn in Inner Mongolia Hetao irrigation district, the reasonable water-saving irrigation scheme in autumn was quantificationally established by using SHAW model in theory, which aimed at the different salinized soils. For slight salinized soils, autumn irrigation quota was from 142 to183 mm between September 28 and October 23. For moderate salinized soils, autumn irrigation quota was from 180 to 200 mm between October 14 and 18. For serious salinized soils, planting sunflower instead of wheat, autumn irrigation quota was from 200 to 225 mm. In the studied irrigation district, autumn irrigation is supposed to be reasonably arranged according to the different salinized soils.

Li R.,Inner Mongolia Agricultural University | Shi H.,Inner Mongolia Agricultural University | Flerchinger G.N.,Northwest Watershed Research Center | Akae T.,Okayama University
Geoderma | Year: 2012

Inner Mongolia Hetao Irrigation District, in north of China, is typical of seasonal frozen soil areas in the region. Irrigation in autumn is required to leach soil salt and to provide a reserve of soil water for the next year's crop. However, improper autumn irrigation results in the secondary salinization of soil. The objective of this study is to simulate soil water and heat dynamics during winter period with the one-dimensional Simultaneous Heat and Water (SHAW) model to assess its capability for simulating overwinter water storage. SHAW model soil parameters were calibrated by data of 1995-1996 and 2002-2004 and validated by data of 1996-2001 and 2005-2006 using field measured soil water contents and temperatures during freezing and thawing periods. Using calibrated and validated soil parameters, the paper simulates the process of soil freezing-thawing, and the dynamic variation of moisture-heat transfer, including soil water content, temperature, frost depth, soil evaporation, and water flux in the seasonal freezing-thawing period. These are useful to determine proper autumn irrigation management, and can be used in future research to address overwinter solute migration to reduce soil secondary salinization. © 2012 Elsevier B.V.

Alkhaier F.,University of Twente | Su Z.,University of Twente | Flerchinger G.N.,Northwest Watershed Research Center
Hydrology and Earth System Sciences | Year: 2012

The possibility of observing shallow groundwater depth and areal extent using satellite measurements can support groundwater models and vast irrigation systems management. Moreover, these measurements can help to include the effect of shallow groundwater on surface energy balance within land surface models and climate studies, which broadens the methods that yield more reliable and informative results. To examine the capacity of MODIS in detecting the effect of shallow groundwater on land surface temperature and the surface energy balance in an area within Al-Balikh River basin in northern Syria, we studied the interrelationship between in-situ measured water table depths and land surface temperatures measured by MODIS. We, also, used the Surface Energy Balance System (SEBS) to calculate surface energy fluxes, evaporative fraction and daily evaporation, and inspected their relationships with water table depths. We found out that the daytime temperature increased while the nighttime temperature decreased when the depth of the water table increased. And, when the water table depth increased, net radiation, latent and ground heat fluxes, evaporative fraction and daily evaporation decreased, while sensible heat flux increased. This concords with the findings of a companion paper (Alkhaier et al., 2012). The observed clear relationships were the result of meeting both conditions that were concluded in the companion paper, i.e. high potential evaporation and big contrast in day-night temperature. Moreover, the prevailing conditions in this study area helped SEBS to yield accurate estimates. Under bare soil conditions and under the prevailing weather conditions, we conclude that MODIS is suitable for detecting the effect of shallow groundwater because it has proper imaging times and adequate sensor accuracy; nevertheless, its coarse spatial resolution is disadvantageous. © 2012 Author(s). CC Attribution 3.0 License.

Alkhaier F.,University of Twente | Flerchinger G.N.,Northwest Watershed Research Center | Su Z.,University of Twente
Hydrology and Earth System Sciences | Year: 2012

Understanding when and how groundwater affects surface temperature and energy fluxes is significant for utilizing remote sensing in groundwater studies and for integrating aquifers within land surface models. To investigate the shallow groundwater effect under bare soil conditions, we numerically exposed two soil profiles to identical metrological forcing. One of the profiles had shallow groundwater. The different responses that the two profiles manifested were inspected regarding soil moisture, temperature and energy balance at the land surface. The findings showed that the two profiles differed in three aspects: the absorbed and emitted amounts of energy, the portioning out of the available energy and the heat fluency in the soil. We concluded that due to their lower albedo, shallow groundwater areas reflect less shortwave radiation and consequently get a higher magnitude of net radiation. When potential evaporation demand is sufficiently high, a large portion of the energy received by these areas is consumed for evaporation. This increases the latent heat flux and reduces the energy that could have heated the soil. Consequently, lower magnitudes of both sensible and ground heat fluxes are caused to occur. The higher soil thermal conductivity in shallow groundwater areas facilitates heat transfer between the top soil and the subsurface, i.e. soil subsurface is more thermally connected to the atmosphere. For the reliability of remote sensors in detecting shallow groundwater effect, it was concluded that this effect can be sufficiently clear to be detected if at least one of the following conditions occurs: high potential evaporation and high contrast between day and night temperatures. Under these conditions, most day and night hours are suitable for shallow groundwater depth detection. © 2012 Author(s). CC Attribution 3.0 License.

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