How to reduce leakage for a small rain pond

I recently dug a hole in a specific location I knew would produce a rain pond. After a week or so, the water usually dries up or heads south into a discharge gully on the edge of the property. I'd like to intercept that if I could.

Thankfully, it rained a lot recently and I got a first taste of how much water it can hold. Not much, but it's a damn nice start. I got a lot of water up hill in swales and paths, so I feel my system is starting to come together.

I'm building a hugelkulture on the south edge of it.

I'm also trying to do both the pond an hugelkulture in a slow and long-term manner, building it step by step, little by little.

Today I enlarged the pond a little and started to wonder if I could slow the water a little more by adding some bentonite or something else.

I read about gley or manure tricks, but I'm not sure I want to go that route. Seems like a lot of work. And I don't have pigs, so that won't work.

Then i heard about putting kitty litter in it. But I'm not sure I want to be throwing chems below my hugelkulture. So, is it advisable to put sodium bentonite in the pond? How much? - the pond is less then 5 meters square and in the end will be about 1m deep on the deep end and on the shallow end flush with the topsoil.

My soil is heavy clay and holds water pretty well, so I imagine I'd need just a little. And I don't want to stop the water, I just want it to slow down enough to pump it back up hill multiple times during a rainy period.

As I'm doing this in a slow and patient manner, the SB technique appeals to me, because I could add a little and see if that helps with retention and add a little more later. Do I have to keep adding it?

Is Sodium Bentonite okay to use in general? Or is it a cost thing?

Cat litter really appeals to me because I have a friend with cats. Supposedly she uses something that is "organic" or otherwise advisable for healthy cats and people, so I maybe could use that - minus the cat poop hhehehe.

As the pond is on the final edge of the property, I'm not too concerned about chems. 200 meters away a guy is spraying shit all over the place so I don't think he'll mind either.

Thanks a bunch,
William

Not all kitty litter is the same. Some are made from bentonite clays (but not necessarily sodium bentonite).
Probably depends on availability and price where it is 'manufactured'.
Quite often, the cheapest ones are those without the chemical 'deodorizers' in them.

For clay soils, approximately 5-7 kilos of bentonite per square metre should do it.

Here is a site that should provide you with the info you need to treat your pond:
http://www.jpself.com/bentonite.htm