This is a tale of two countries - one landlocked, with two-thirds of its harsh environment given over to desert and where rainfall is thought to be reducing; the other low lying, with millions of inhabitants squeezed onto narrow spits of land prone to severe monsoon flooding.
They may be continents apart, each with their own set of problems, but in both, girls miss out on school because they spend hours fetching water. Mothers give birth with no access to clean water. Children are dying from chronic diarrhoea. Livelihoods are put on hold through illness and hospital beds are full.
Water is life. That might sound hackneyed, but believe me there has never been a more potent truism - especially when today, World Water Day, there are still nearly 900 million people across the world who don't have access to a safe water supply.
If, as is widely predicted, global temperatures increase by around 2C, up to 3 billion more people will experience water stress. In a chilling report published by Save The Children last year, climate change will more than treble the number of people caught up in natural disasters in the next 20 years.
Let's go back to the first of our two countries. Here, in an arid eastern corner, villagers are forced to migrate as far as the neighbouring country in search of water for themselves and their cattle during the six-month dry season. These semi-nomadic people rely on their cattle for every aspect of their lives. The womenfolk trudge ever-increasing distances across the desert to a series of large holes that the community dig in order to catch the rain water each year. These holes run dry after a couple of months, and anyway, the water isn't safe to drink.
WaterAid is working alongside the people here to help them survive the dry seasons and more frequent droughts by using simple, locally sourced and maintained technologies such as rainwater-harvesting tanks and micro-dams. Communities are involved at every stage of the process, from planning to building and upkeep. Through self-help, citizens take action by managing the standpipe or well in their area and by introducing straightforward hygiene practices to mitigate against disease.
The chief in one village is philosophical about the situation: "Together we can develop our community. You have to keep tradition, with one hand you must reach into the future, with the other you must keep it in the past."
Now let's take our second country, where the population is grappling with a very different scenario. Over-abstraction from rivers and groundwater means that water tables are dropping, while saline intrusion and the natural presence of arsenic are making matters worse still. With increasing floods, pit latrines overflow and pollute the wells. Waterborne diseases are rife and treating contaminated water is costly.
Freshwater resources are highly sensitive to variations in weather and climate change - flooding in the capital city a few years ago left it swimming in sewage and submerged under filthy water for weeks. When the monsoon rains come, communities living on precarious sandbanks in the deltas are often forced to abandon their homes and move on. Annual cyclones leave whole villages deluged in saline water and people in dire need of safe drinking water.
If, as predicted, the sea level rises, the water line may be brought further inwards thereby aggravating the situation; storm surges could potentially cause significant casualties and destroy existing infrastructure including water supply and sanitation.
So where are our two countries? In this instance they are Mali and Bangladesh. But the sad truth is that they could just as easily have been Burkina Faso and India, Niger and Mozambique, Ethiopia and Nepal. And as is too often the case in such countries, it is the most vulnerable community members who suffer the most: the elderly who are too frail to relocate; people with a disability who need specially adapted latrines; young children struck down with diarrhoea.
In a situation of climate volatility, supply of and control over water is made more acute. This World Water Day, we have an opportunity to change the lives of the poor before climate change exacerbates their suffering. Governments need to strengthen health, water and sanitation systems so that they are ready to cope with the effects of climate change and developing countries must also draw up plans for climate change adaptation. We know all this is possible - it just needs leadership and political will.