Will walnut tree litter kill pond?

My swimming pool has been established for over 20 years on city. Water and rain water (none from the roof). It has had leaves to clean but fewer this year. However three walnut trees have dropped some this their first year of fruiting. We skim and use a cover regularly with very little litter or refuse. After last weeks heat I uncovered the pool to find an unbelievable stench of amonia and dark brown/black water (very little refuse on the bottom or in the water. We used baking soda, chlorine tablet (big) and flocculant and the sand filter for 24 hours. We had used this recipe before for stubborn effluvia and algae. Today the water is light green/brown and we can see to the bottom. Pool is not covered. Few leaves to skim. Will this water kill me and my cocker spaniel? It seems to help her allergic skin when she swims and is bathed in it. Hedy