Based on the appalling facts, that in 2000 1.1 billion people lacked access to improved drinking water and 2.4 billion were without basic sanitation, the Millennium Development Goals (MDGs) defined specific water and sanitation targets: "to halve, by 2015, the proportion of people without sustainable access to safe drinking water and basic sanitation".

To assist the international community in achieving the water and sanitation targets of MDG 7, United Nations Secretary-General Kofi Annan announced the establishment of the Advisory Board on Water and Sanitation at World Water Day in 2004 (press release). Former Japanese Prime Minister, Mr. Ryutaro Hashimoto, agreed to serve as Chairman of the Board. Its members were chosen for their proven experience in providing inspiration, moving the machinery of government, and working with the media, the private sector and civil society. When Mr Hashimoto passed away, His Majesty King Willem-Alexander (then His Royal Highness the Prince of Orange) took over and chaired the Board until he ascended the throne in April 2013. His Royal Highness Prince El Hassan bin Talal of Jordan followed but had to leave the Chair position in April 2014 in order to dedicate his time towards Middle Eastern affairs. Dr Uschi Eid, Vice-Chair of the Board from its inception, chaired the Board during its final period.

The UN Secretary-General's Advisory Board on Water and Sanitation (UNSGAB) was an independent body set up to galvanize global action on the Millennium Development Goal targets for drinking water and sanitation.

Recognizing that these two targets only covered a small bit of the overall water and sanitation challenges and that addressing them would be critical for achieving the overall MDG agenda, UNSGAB decided early on to broaden its mandate to key water and sanitation issues not addressed by the MDGs. These included: water quality and pollution prevention, financing of water, IWRM and Nexus, and water-related disasters.

The Board focused its work on:

• give advice to UN Secretary General on water and sanitation challenges
• publicly mobilize support, advocate for actions and ensure political visibility
• advocate for improving the capacity of governments and the international system
• give input to relevant global dialogue processes
• raise global awareness through all available media and other channels
• influence and work with global, regional, national institutions at highest level
• assess progress made towards the water and sanitation targets
• help to mobilize resources for water and sanitation towards achievement of the MDG water and sanitation targets.

At the beginning of its work, the Board decided to carry out these tasks not by producing new studies, but by analysing existing declarations and commitments and by catalysing actions towards the most pressing challenges. To devise and structure its work, the Board developed three consecutive Hashimoto Action Plans (HAPs), so-named in commemoration of the late Ryutaro Hashimoto:

• Hashimoto Action Plan I, launched at the World Water Forum in Mexico in March 2006
• HAP II, launched in January 2010
• HAP III , launched at the Budapest Water Summit in October 2013.