The Invesco Water Resources ETF (PHO) aims to mirror the performance of the NASDAQ OMX US Water Index. This fund typically allocates at least 90% of its total assets to equity securities, including common stocks, American Depositary Receipts (ADRs), and Global Depositary Receipts (GDRs), issued by US exchange-listed companies. These companies are identified by the index as crucial to the water industry, specializing in products and services for water conservation and purification across residential, commercial, and industrial sectors.