In order to increase opportunities for Indian tribes to develop, manage, and protect their water resources, in fiscal year 2003 and thereafter, the Secretary of the Interior, acting through the Commissioner of the Bureau of Reclamation, is authorized to enter into grants and cooperative agreements with any Indian tribe, institution of higher education, national Indian organization, or tribal organization pursuant to sections 6301 to 6308 of title 31. Nothing in this Act is intended to modify or limit the provisions of the Indian Self Determination Act [25 U.S.C. 5321 et seq.].