Water. Without it, nothing would happen. It is first a prerequisite for life; it underpins every element of human development. Without it we cannot produce food, harness energy or sustain a productive economy. Yet there is no other resource so much taken for granted.
Water for development is the theme of this year's World Water Week in Stockholm. We all know a country can only develop fully if all of its population has access to water and sanitation. Taps and toilets transform people's life chances, leading to better health, education and economic opportunities. It is fundamental to eradicating extreme poverty and to women and girl's empowerment.
Yet in this hyper-connected, tech-savvy, fast-moving world, the figures show we are still not giving water and sanitation the prioritisation needed. More than 650 million people, or around one in 10 of the global population lack access to improved water, and one in three lack access to basic sanitation.
Rapidly developing economies are increasingly realising that a healthy workforce and the boosted productivity that brings, and an economy that is attractive to investors, are impossible without basic services such as drinking water and sanitation. The total global economic losses due to inadequate water supply and sanitation services have been estimated at $260 billion a year .
On a recent visit to Madagascar, I saw one example of how meeting this basic need can put a community on the road to development. I travelled to the rural town of Mahasolo, which lies about 100 kilometres north of the capital Antananarivo. Until 2012, none of its 11,000 inhabitants had access to clean water and half the population had to go to the toilet in the open. On average the girls in the village would spend around six hours a day collecting water, leaving little - if any - time to go to school. It's a familiar story across the rest of the country, where nearly half of Madagascar's population lives without access to safe water and a decent toilet.
13-year-old Francine, washes her face at the handwashing station at her school in the Menabe region, of Madagascar. WaterAid/ Ernest Randriarimalala
Thankfully for the people of Mahasolo, that's now changed. With the help of WaterAid's local partners, taps and toilets have been installed, and the improvements are clear. Girls are able to go to school and they told me how they were able to manage their periods and menstrual hygiene since the schools now had good facilities and a supply of sanitary products. Women have more free time to start their own businesses and earn a living, and the risk of water-borne diseases has decreased. The town now has greater economic freedom and prosperity than it did three years ago. The town's story is an echo of every community around the world that gains sustainable, reliable access to safe water and sanitation.
Madagascar is a long way from Stockholm, but these are themes WaterAid will visit over the course of the week. In panels on Water for Women, and how to address gender equality in the new Sustainable Development Goals, we'll examine how women and girls are disproportionately affected by the water and sanitation crisis.
We will explore the important role water and sanitation play in health, with the launch of a new World Health Organization strategy on tackling neglected tropical diseases including blinding trachoma and intestinal worms, through action on water, sanitation and hygiene - a strategy which WaterAid, alongside other organisations, has played a key role in developing.
We'll hear from developing world governments and the Sanitation and Water for All coalition on how to build water and sanitation systems that last, and the roadblocks along the way. And we'll discuss with our partners and peers some of the new advances, and new challenges, in our work, which now spans 37 countries, including how to make our programmes more resilient to the increasing challenges of climate change, and how to incorporate mobile phone technology into mapping water points to make our work more sustainable.
This year's Stockholm World Water Week is the 25th time the city has hosted this important week of examination, reflection, knowledge-sharing and celebration of innovation. The theme, Water for Development, also reflects the critical timing around how our world approaches development and the fight to end extreme poverty.
Next month world leaders will meet at the UN General Assembly in New York to endorse a set of new goals, which if they are met will transform the world over the next 15 years. The new Sustainable Development Goals (SDGs) will commit the global community to universal access to water, sanitation and hygiene by 2030.
Achieving this goal will play a fundamental role in consigning extreme poverty to the history books.
We have made progress since that first World Water Week in 1990. More than 90% of the world's population now have access to an improved source of drinking water, and 2.1billion people have gained access to basic toilets.
But we know this progress has been uneven - leaving out the poorest, most remote, the elderly, the disabled and other marginalised people - and that there is so much more to be done.
Children on their way back to school with buckets full of dirty water in the Moramanga region of Madagascar. WaterAid/ Ernest Randriarimalala
This year represents a unique opportunity for the global community to commit afresh to doing more and to do it better. Governments, the private sector and civil society all have critical roles to play.
Change takes time, and the global community has just 15 years to keep a promise to the world's poorest and most vulnerable - that no longer will their health, dignity and prosperity be limited for lack of water, basic toilets and good hygiene.
Stockholm World Water Week represents a chance to renew our energy to keep these promises, and redouble our efforts to reach everyone everywhere by 2030.