Install a rain barrel under the downspout that is producing runoff from your roof. You can purchase rain barrels or make them yourself out of 55-gallon plastic barrels or watertight wine barrels, with faucets and various hardware added. Rain barrels also provide you with water to irrigate gardens and for other outdoor water needs.
Add a flexible downspout to divert the water away from the bubbler fountain. Ensure that the water is running away from the house foundation downhill toward a retention pond or storm drain. Flexible downspouts vary -- some are attached with clamps to the metal downspout while others fit snugly onto the downspout.
Slope the ground around the bubbler fountain so that rain runoff diverts naturally around the fountain. The grade doesn't have to be extreme -- the minimum is 6 inches for every 10 feet of slope -- and you can do this by simply mounding soil around the base of the fountain with a spade.
Choose a location in your yard that is between the source of the rain runoff and the bubbler fountain.
Dig out the area for your proposed rain garden to slope down 4 or 6 inches in depth at the center.
Plant native plants in your rain garden. These plants are suited to your geographic location and have strong root systems that will catch the rain runoff. Many rain garden plants do well in both wet and dry soils to account for varying rainfall. Examples of rain garden plants include rattlesnake masters, downy sunflowers, cardinal flowers and sedges. Plants take a few years to become established; however, you may be able to find mature plants for a higher price. If you have thriving natives on your property, you can transplant them into your water garden.