I intend to conduct a study in the Tigris and Euphrates basins. I am eager to cooperate with anyone who has a long-term series of data and information about this basin. Please do not hesitate to contact me.
I would like to suggest you explore global datasets; you could find a vast number of climatic, crop, and hydrological datasets. However, these are inaccurate but still are useful in data-scarce regions.
There are number of websites that offer freely/publicly available historical meteorological and streamflow datasets. Links for few of them I have mention below:
However, for detailed information, you can go to the page (link mentioned below) where I have compiled several websites and sources to get streamflow and meteorological datasets of the respective regions you may require: