I’m sure the front cover and illustrations were in autumn colours. It’s about a little girl who goes to the park, manages to fall into the pond, but is rescued by the park keeper. It’s definitely a children’s book, with more pictures than text.
I’ve probably made it sound like a grim near-drowning incident (!) but it was actually a lovely story about the kindness of strangers. I remember reading it several times in the local library when I was at primary school, but as I can’t remember the title, I’ve never found it since.