Hi Chris, may be you could read about the application of satellite-based algorithms to estimate the regional ET. Try on isiweb of knowledge using the key words: SEBAL, METRIC, S-SEBI combined with "riaprean. Please let me know about your results. Cheers.

Hi marcos. Thanks for your impulse. I will give it a try. Cheers

Hi Christian, I have recently read a paper about riparian vegetation and its influence on the hydrological cycle. There might be some interesting references..Salemi et al. (2012): Riparian vegetation and water yield: A synthesis.Journal of Hydrology.

thanks vaclav. i flew over the summary and it's defenitely worth reading, presumably useful for the introduction. when it comes to calculation, i have a different access:

the evapotranspiration, as not to be measured (here), should be calculated by using the pm-equation standardized for grassland. due to the investigation area is a riparian area, shadowing might play a role (the representative weather station is affected by shadowing).

evapotraspiration then is an input-parameter for a soil water and nitrate transport model of the unsaturated zone. different types of input-data (nearby weather stations) should indicate the significance of exactly known weather data for modelling soil water and N-export on a regional scale.

cheers

Hi Christian, may be you could calculate the incoming solar radiation based DEM.

Hi yongmin. May you be so kind and specify your input, please.

Here is a paper on how to calculate impact of terrain on surface received solar radiation (Wang, K., X. Zhou, J. Liu, and M. Sparrow (2005), Estimating surface solar radiation over complex terrain using moderate-resolution satellite sensor data, International Journal of Remote Sensing, 26(1), 47-58). You can download it from my directory here.

Thank you for providing it, i am going through at the moment.

Also you could try to find the riparian evaporation using the diurnal changes in the flow and see how it matches the evaporation values by pm

Hi rakesh, as there is obviously no need for exact data in the first way (reasoned by the transport model), i will try to give a good approximation by comparing the riparian-pm-results (with influence of shadowing, because the weatherstation is also affected by shadowing) with those of one (or more) nearby weatherstation based on "clear days" (as a bell-shaped character of solar radiation curve of both stations should be helpful). Should be a quick-and-dirty approach to gain first results.

Hi Cristian,

When radiation data are missing or of bad quality, FAO advises to replace radiation in the PM method by an approximation based on o.a. maximum and minimum temperature (Allen et al. 1998). We tested it in several catchments in Europe (Van Loon et al. 2012, HESS) and results were surprisingly good (Rakovec et al. 2009 and Veenstra et al. 2009; see http://www.eu-watch.org/publications/technical-reports).

Good luck!

Anne

The effect of riparian vegetation may go well beyond shadowing. Please see the following paper which I found fascinating:

Boughton DA, Hatch C, and Mora E (2012) Identifying distinct thermal components of a creek. Water Resources Research 48, W09506. DOI: 10.1029/2011WR011713

The following is an excerpt from page 10 of that paper:

"If the effect of vegetation were purely to shade out insolation (long and short-wave radiation), then the shady reach should decouple from insolation patterns, meaning LDC 3 should be close to zero or perhaps weakly positive. The fact that it is negative suggests a subtraction of heat from the channel water proportionate to the level of insolation. One possible mode of heat subtraction might be heat movement into the bed—for example via hyporheic flows [Acuna and Tockner, 2009; Burkholder et al., 2008]—but one would need to propose a mechanism by which such heat movement stays so closely proportionate to insolation. It is also possible that evapotranspiration of the riparian canopy provides a plausible mechanism for heat subtraction upward, because evapotranspiration tends to produce gradients between leaf surface temperature and ambient air temperature [Alexandridis et al., 2009]. This could set up a net movement of sensible heat

and/or long-wave radiation from the water to the canopy that should stay fairly proportionate to insolation."

Hi anne,

thanks for your advice. Dataset is complete for the investigation area. Time before i tried to calculate et0 and replaced radiation by sunshine duration - also with good results, small underestimation esp. In spring.

Cheers,

christian

There is an interesting series of publications on this topic:

https://www.researchgate.net/publication/220649829_A_comparative_analysis_of_DEM-based_models_to_estimate_the_solar_radiation_in_mountainous_terrain

http://www.researchgate.net/publication/258073381_A_High-Resolution_Topographic_Correction_Method_for_Clear-Sky_Solar_Irradiance_Derived_with_a_Numerical_Weather_Prediction_Model

http://www.researchgate.net/publication/251524957_A_topographic_geostatistical_approach_for_mapping_monthly_mean_values_of_daily_global_solar_radiation_A_case_study_in_southern_Spain

http://www.researchgate.net/publication/255218734_Spatial_disaggregation_of_satellite-derived_irradiance_using_a_high-resolution_digital_elevation_model

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