Dear Newton,

You mention that you already calibrated and validated SIMHYD using historic data probably by comparing observed discharge series (Qobs) and simulated discharge series (Qsim). The next step might be to use the (downscaled) output of the Global Climate Model (GCM) for a historic period (e.g. 1971-2000; Qhis) to assess the performance of the combination of downscaled GCM data and SIMHYD in simulating the discharge statistics. Next, the runoff under climate change can be assessed using downscaled GCM output for the periods 2019-2039 and 2040-2069 (Qfut). The differences between Qobs and Qsim are mainly caused by the hydrological model, the differences between Qsim and Qhis by the difference in climatic input (downscaled GCM data) and the difference between Qobs and Qhis by both the hydrological model and climatic input. The difference between Qhis and Qfut will give you the impact of climate change on runoff.

The runoff projections under climate change cannot be calibrated or validated. However, some insight in the proper functioning of the model can be obtained by carrying out the previous comparisons and, if possible, looking at past climatic changes and how the model simulated the impacts of those changes.

Good luck and regards,

Martijn

Dear Newton Muhury,

In similar studies, the rainfall runoff field, the catchment is implicitly assumed not changed. This means you do not need to re-calibrate your model if we think a model as a representation of a catchment. Then, the only thing is to drive your calibrated model using past, current and future forcing data and analyze the results. The analysis depends on your research purposes. You can pay attention to the changes of flood peak, runoff volume, and so on.

Regards，

Minjiao

Matijn and Minjiao answers have covered your question well. To add to that, I recommend reading recent studies on how this is done. Below are a couple of my articles.

Article Climate change and land use impacts on hydrologic processes ...

Article Effect of Climate Change on Watershed System: A Regional Analysis

Hi

There is no much to add to Martjin's answer. You simply use the rainfall and PET calculated from CMIP5 to feed the model and the resulting runoff will be for the future which has to be compared to a baseline simulation using inputs from the same climate models for a historical period and not your calibration simulation; simply because the climate models will still have some bias which is assumed to remain in the future. Are you just using the ensemble mean from CMIP5 or using individual members of the ensemble? The latter will give you some handle on the uncertainty resulting from climate models. The absolute minimum is to have 3 members, two extremes and one in the middle but the more you use the better. There are method to select these members that you need to use. Basically models that perform better for the baseline are selected. Additionally, they need to span the range of uncertainty in the future for the variables considered (PET and rainfall).

I would stress what Martijn mentioned that you need to consider downscaling as GCMs are usually too coarse for rainfall-runoff modelling at the catchment scale.

Scan the literature before proceeding.

Dear Martijn, Minjiao, Timothy, Arash and Ezzat,

Thank you all for your input. I specially thank Matijn to explain in clear text how to use projected data in SIMHYD. Thanks

Timothy, could you please send me the full text of the articles to read. Thanks

Regards

Newton

Hi Martijn,

Do you know is there any way to convert .nc file to csv file format? How can I edit .nc file before using in the SIMHYD model? Thanks

Hi Newton,

I don't know how you can convert .nc files to .csv format. Maybe another colleague knows this.

For your information, below is an article where we did the comparisons between different simulated streamflow series (as mentioned before) for a study on low flows.

Hi Martijn,

Thank you for the article.

I am trying to download CMIP5 data from https://esgf-data.dkrz.de/projects/esgf-dkrz/

Do you know how can I download data for Australia or is there any way we can use latitude and longitude for projection? Thanks

Regards

Newton

Hi Newton,

You might ask one of the contact persons of the download website/ portal? As far as I know you can select specific areas using latitudes and longitudes and/ or zoom options.

Regards,

Martijn

Hi Newton,

nc format is a 2D or 3D geographical format including some self description of the contents. There is a variety of tools to process it and visualize it. One nice program to visualize it is Panoply: https://www.giss.nasa.gov/tools/panoply/

Many of the GIS packages (e.g. the free QGIS) will read nc files as mutli-band rasters and you can use these to clip the region you need and convert them to other raster format, e.g. Ascii - which you can further process to csv.

To process the data, you can also use matlab or the very efficient command line program "cdo" but that may require switching to Linux or installing cygwin to run on windows: https://code.mpimet.mpg.de/projects/cdo/files

Subsetting the data spatially or temporally is done very easily in CDO. Matlab (and may be R) can help you do whatever processing and format conversion. You need to know the file structure of the nc file, tools like panoply and cdo are very helpful.

Hope this helps,

Mohamed

Hi Newton,

You can convert .nc to .csv in many ways e.g. through some ways as Mohamed has mentioned. In addition, there is add-in tool in M. Excel called netcdf4excel (https://code.google.com/archive/p/netcdf4excel/) that may help you to convert .nc files into .csv or .xls or else.

However, based on my experience, the main problem of working with GCM/RCM dataset is not about converting from .nc file to other formats, but rather working with (very) large dataset. It can be a tedious work if you want to convert the .nc files that are often stacked per month (a single .nc file encloses daily climatic data of a month), per point/grid location, per climate variable and per climate change scenario (e.g. RCP 4.5 or 8.5). For this reason, it is better to work with the .nc files first before you convert into other formats by means using script (e.g. from wget tool) to automate the works (e.g. download .nc files covering all time-length and grids of your study area, combine into single .nc file containing all climate variables you observed, etc.).

Good luck!

If you already calibrated and validated the model for current climate, you can use this configuration for the future climate. For the simulation of the future be careful with the potential variability respect to the current conditions (other than rainfall, Temp, PET) as: land use, land cover, erosion, snow volumes, morphology changes, etc.