white bathtub rings on canyon rocks showing drought conditions, lake mead, arizona nevada border at hoover dam, usa

america american are arizona attraction bathtub blocks border canyon change climate colorado concrete conditions dam desert destination dropping drought dry end environment flow from generation henderson high hoover hydro hydroelectric imposing intake into jutting lake las levels low mead nature nevada north reservoir rings river road rocks rocky shortage shortages showing side south southern southwest southwestern states structure tourism tourist towers united usa vegas water west western where white