Title of the dataset:
	Inputs for lake morphology in ISIMIP3 runs of the global lake sector

Creators:
	Rafael Marcé		ORCID: 0000-0002-7416-4652
	Catalan Institute for Water Research (ICRA) ​
	
	Daniel Mercado		ORCID 0000-0003-4572-3029 
	Catalan Institute for Water Research (ICRA)

	Inne Vanderkelen	ORCID 0000-0002-8673-1933
	Vrije Universiteit Brussel

Contributors:
	Maddalena Tigli
	Iestyn Woolway
	Annette Janssen
	Benjamin Kraemer
	Mahtab Yaghouti
	Sebastiano Piccolroaz
	Wim Thiery
	Don Pierson

Related publication:
A framework for ensemble modelling of climate change impacts on lakes worldwide: the ISIMIP Lake Sector

Malgorzata Golub, Wim Thiery, Rafael Marcé, Don Pierson, Inne Vanderkelen, Daniel Mercado, R. Iestyn Woolway, Luke Grant, Eleanor Jennings, Jacob Schewe, Fang Zhao, Katja Frieler, Matthias Mengel, Vasiliy Y. Bogomolov, Damien Bouffard, Raoul-Marie Couture, Andrey V. Debolskiy, Bram Droppers, Gideon Gal, Mingyang Guo, Annette B. G. Janssen, Georgiy Kirillin, Robert Ladwig, Madeline Magee, Tadhg Moore, Marjorie Perroud, Sebastiano Piccolroaz, Love Raaman Vinnaa, Martin Schmid, Tom Shatwell, Victor M. Stepanenko, Zeli Tan, Huaxia Yao, Rita Adrian, Mathew Allan, Orlane Anneville, Lauri Arvola, Karen Atkins, Leon Boegman, Cayelan Carey, Kyle Christianson, Elvira de Eyto, Curtis DeGasperi, Maria Grechushnikova, Josef Hejzlar, Klaus Joehnk, Ian D. Jones, Alo Laas, Eleanor B. Mackay, Ivan Mammarella, Hampus Markensten, Chris McBride, Deniz Özkundakci, Miguel Potes, Karsten Rinke, Dale Robertson, James Rusak, Rui Salgado, Leon van den Linden, Piet Verburg, Danielle Wain, Nicole K. Ward, Sabine Wollrab, and Galina Zdorovennova

Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2021-433, 2022
        

Description:
What is the goal of this research? 		- To study the effect of climate change on lakes using a multi-model approach. 
What kind of data did you collect or produce? 	- This repository produces the basic morphological lake data to be input to the lake models participating in ISMIP3 simulations
How was the data produced? 			- The lake input data stored in thsi repository is a elaboration of data in available databases on lake location and morphometry 

General description:

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a single model forced with limited scenario-driven projections of future climate for a relatively small number of lakes. As a result, our understanding of the effects of climate change on lakes is fragmentary, based on scattered studies using different data sources and modelling protocols, and mainly focused on individual lakes or lake regions. This has precluded identification of the main impacts of climate change on lakes at global and regional scales and has likely contributed to the lack of lake water quality considerations in policy-relevant documents, such as the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). The Lake Sector of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) was founded for simulating climate change impacts on lakes using an ensemble of lake models and climate change scenarios. The protocol prescribes lake simulations driven by climate forcing from gridded observations and different Earth system models under various Representative Greenhouse Gas Concentration Pathways, all consistently bias-corrected on a 0.5° × 0.5° global grid. The ISIMIP Lake Sector is the largest international effort to project future water temperature, thermal structure, and ice phenology of lakes at local and global scales and paves the way for future simulations of the impacts of climate change on water quality and biogeochemistry in lakes.

For a comprehensive description of ISIMIP, sectors, and protocols please see https://www.isimip.org/

In order to simulate the impacts of climate change on lakes worldwide, the ISIMIP3 Lake Sector protocol has defined a set of lakes to be modelled by all participating lake models, as well as the basic morphometry (i.e., hypsographic curves) information for each lake. This repository includes all calculations performed to obtain the final set of lake location and mosphometry inpput information for ISIMIP3 runs. For this, available datasets on global lake extension and morphometry were used first for selecting a set of representative lakes on Earth (~40000 lakes, one for each 0.5º pixel of the normalized input/putput grid for ISIMIP across sectors), and then morphological characteristics were assigned to each representative lake using a database on global lake morphology. The final set of files constitute the input data for lake morphology and location for ISIMIP3 Lake Sector runs, which are produced in netCDF format.

   

Keywords:
Lake Morphology
Climate change
Lake thermal structure
Input data
Global

Software:

To run the scripts in this repository you need R (at least version 3.0.0) and Phyton3. There are several libray dependencies as stated in the relevant scripts.

Explanation of variables:

# Inputs for lake morphology in ISIMIP3 runs of the global lake sector
## Method implemented to obtain the lake collection and morphology inputs for ISIMIP3 simulations in global lakes
### This is a brief guide to follow the steps implemented, if you want more details please check the three folders containing the full calculations:

**[lake_identification]:** selection of the representative lake for each pixel. We took the 1.4 million lakes in [HydroLAKES](https://www.hydrosheds.org/pages/hydrolakes) and calculated the depth weighted median (weighted by area of the lakes) for all the lakes contained in each pixel with a 0.5º resolution. 
**[Hypsographics]:** we extract the Volume, Area, mean and maximum Depth, and hypsographic curves from [GLOBathy](https://www.nature.com/articles/s41597-022-01132-9) (find here [repository](https://springernature.figshare.com/collections/GLOBathy_the_Global_Lakes_Bathymetry_Dataset/5243309)) for each representative lake selected in the previous step, using the lake ID to cross reference the two databases (GLOBathy and HydroLAKES use the same id attribute). 
**[create_netcdf]:** Phyton scripts to produce the final netcdf files available in [inputs_ISIMIP_netcdf]

**[Water_area_per_pixel]:**: Under development. Will contain the fraction of each pixel covered by lakes present in the HydroLAKES database. 

### Folders containing the lake morphology inputs for ISIMIP3 sumulations in the global lakes sector 

**[inputs_ISIMIP3_netcdf]:** Final collection of inputs for the ISIMIP3 runs of the global lake sector in netcdf format. THESE ARE THE RECCOMENDED FILES TO USE. See the Readme.md file in the folder for further details.

**[inputs_ISIMIP3]:** Final input datasets in raster and shapefile format. In this folder you will find information in raster and shapefile format on the representative lakes per pixel, basic morphological features for each lake, and hypsographic curves. PLease, consider there is no supporting metadata for these files, so we reccommend using the netcdf collection at [inputs_ISIMIP3_netcdf] 

## Summary of the approach

The representative lakes is a collection of lakes to be used for global lakes ISIMIP3 runs. There is one lake per 0.5º pixel, and the final selection was the result of a procedure that tended to pick conspicuous lakes in the landscape (in terms of both area and depth). You will find an assessment of the implications of our choice in the folder [Hypsographics/GLOBathy]. The final set considers 41449 lakes, one per pixel. Very big lakes occupying more than one pixel are associated to one single pixel as well, but the area and volume information stored in that pixel refers to the whole lake. We have included two files (biglakes_mask.nc, hydrolakes_id_biglakes.nc) in case you want to plot the results of very big lakes on their real extension, not just one pixel. We have included those files to help producing plots that would look realistic (i.e., with very big lakes conspicuous in a global or regional map), but we urge modellers to use the original approach (1 lake, 1 pixel) for statistical analyses of the results.

You can identify each representative lake with the hydrolakes_id.nc. Since this variable stores the Lake ID used in HydroLAKES, all attributes in this database can be easily recovered. Please, be mindful that representative lake definition in ISIMIP3 selected real lakes included in HydroLAKES, therefore the representative lakes in ISIMIP3 ARE NOT a statistical construct, but an actual lake in the landscape.    

For the morphology of each representative lake, we included information to allow calculations considering different sources of information. Modellers can pick the method more suited to the model to be applied:

1. Hysographic curve: this must be the default method if your model accepts an hypsographic curve as an input. We have included a level-area and a level-volume hypsographic curve for each of the 41449 lakes. Each hypsographic curve consist of 11 data pairs relating level (bottom of the lake as the reference) with area or volume. This is stored in hypso_area.nc and hypso_volume.nc. 
 
2. We also included a power law fit of the previous hypsographic curves, defining the relationship between level (bottom of the lake as the reference) and area or volume. Those fits are generally good, but deviations from the reference hypsographic can be large in some cases. We reccommend using the hypsographic curve whenever possible. This is stored in area_fit.nc and volume_fit.nc. 

3. If an hypsographic curve cannot be input to your model, we also offer information on lake total volume, maximum area, and mean and maximum depth. You will need an assumption of lake shape (cyclyndrical, conical, etc.) to use this approach. You will find the corresponding netcdf files in [ISIMIP_Lake_Sector/inputs_ISIMIP3_netcdf/Basic_inputs] 


References:
[HydroLAKES](https://www.hydrosheds.org/pages/hydrolakes)
[GLOBathy] [repository](https://springernature.figshare.com/collections/GLOBathy_the_Global_Lakes_Bathymetry_Dataset/5243309)-[article](https://www.nature.com/articles/s41597-022-01132-9)


This dataset is published under the CC BY (Attribution) license.
This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator.


