Hi Dissanayaka, the erro is basically telling you there is a problem in the format of the slr.slr file in the textinout folder in your ArcSWAT project file.
1. Check the length of time of the slr.slr data.
2. If you have missing data, check if the missing format meet the correspond to the SWAT format for slr.slr file. eg. change -0099.000 to -099.000 since slr file format is xxxx.xxx . If this is the case, you will have to make changes to your pcp1.pcp (xxx.x) file, hmd.hmd (xxxx.xxx) file and wnd.wnd (xxxx.xxx) file.
I am getting the same error and I have tried changing the format for missing values too but it is still not working and same error is coming again. any guide how to solve it?