Efforts have been under way to restore wetlands along the San Joaquin River as well as on the historic shores of Tulare Lake. These primarily entail the cleanup of existing wetlands and procuring additional water supplies, rather than converting agricultural land back into the original swamp and marsh. Since wetlands can provide a natural form of flood control – wetlands act like sponges, absorbing flood flows during the rainy season and releasing the accumulated water during the dry season – and also can filter out many forms of toxins, especially from fertilizers, they are important to maintaining good water quality in the San Joaquin River. Wetlands preservation group Ducks Unlimited was awarded a $1 million grant in 2005 as part of the North American Wetlands Conservation Act in order to conduct restoration work on of swamps and marshes throughout the San Joaquin Valley.