Nearly two-thirds of the world’s population experiences some level of water scarcity—and an estimated one billion urban residents face unreliable drinking water supplies. This global water crisis not only has been recognized by the United Nations, but also prioritized for action as Sustainable Development Goal (SDG) 6: “Access to Water and Sanitation for All”.

Yet participants in the United Nations 2023 Water Conference determined that the ability to meet those SDG 6 objectives was severely off track. The Blueprint for Acceleration Synthesis report from the conference identifies significant obstacles to progress, including “not enough money, not enough data and not enough innovation.”

One area that has been both poorly researched and little understood in the global water security field is the role played by informal water markets, particularly tanker water markets (TWMs). These water deliveries by privately operated tanker trucks are increasingly relied upon to reallocate water from rural areas to urban users. Informal TWMs have been critical, especially during extensive droughts, as a means to provide water in major cities, such as Chennai, Nairobi, and Mexico City.

The importance of understanding the role TWMs play in urban water security is increasingly being recognized. Yet there has been only limited data collected on these informal institutions, whose implicit goals are to elude penalties imposed for sourcing water illegally and to avoid costly licenses. Thus, open questions remain as to whether TWMs enhance water security; whether their benefits or their negative impacts predominate in practice; and whether or not stronger regulation could improve them.

Our research team has sought to fill in these data gaps. We examined illegal TWMs in Jordan—which provides a quintessential example of a nation heavily dependent on tanker water to help satisfy demand. (Jordan’s highly intermittent public water supply system and rapidly growing population are key elements in that demand.).

Our findings aim to provide decision-makers attempting to accelerate progress on global water security and SDG 6 with answers to important questions: What is the role of illegal TWMs in urban water supplies? What are the impacts of TWMs on declines in groundwater levels? How do TWMs respond to regulation? How will TWMs affect future prospects for equitable water access in increasingly water-stressed supply systems?

Growing Dependence on TWMs is Pervasive and Costly

One key finding in our research is that TWMs sell 10.7 times as much water as official government well licenses permit. This suggests that water users are far more reliant on this informal institution than previously reported.

TWM sales account for 27% of groundwater over-abstraction, contributing to aquifer depletion and impeding the government’s goal to manage aquifers sustainably. Of all the funds that Jordanian households and firms spend on water, TWMs account for approximately 52%. Yet tanker trucks deliver only 15% of household water supply in that country.

In addition, businesses receive 75% of tanker water deliveries. Transporting water via road is terribly inefficient, with approximately 70% of tanker water sales revenue going to transport costs and creating unnecessary carbon emissions.

Cost was another key takeaway from our research. Tanker water is on average 4.8 times as expensive as piped water, but households do depend heavily on it. The consequence of this dependency is that drinking water is much less affordable for households without reliable public water supply.  Indeed, our investigation found that 92% of water-poor households with access to less than 40 liters (approximately 10.6 gallons) per person per day of piped water also purchase tanker water at high prices.

TWMs are competitive markets, however, and their prices reflect the high costs of delivering water by road. High TWM expenditures are a symptom of insufficient access to the much more efficient water distribution via piped networks.

We also discovered that the dependency is increasing. Households’ precarious reliance on tanker water will grow 2.6-fold by 2050. Our analysis suggests that the price of tanker water will trend higher due to three factors: groundwater depletion, expanding transport distances to source water, and increasing demands.

By 2050, the number of individuals receiving less than 40 liters per person per day of public water supply will increase fivefold. Due to the rising prices, only 64% of that vulnerable population will still be able to afford tanker water, compared to 92% now.

Policy Implications: Supply and Regulation 

Results of our research suggest that Jordan’s TWMs present two policy challenges: First, Jordan will have to invest in its public water supply system. The extensive reliance of households and firms on water deliveries via truck reveals just how tenuous piped water access in Jordan already is. And as groundwater levels fall and tanker prices rise, this supply source of last resort will cease to be affordable for many households, severely exacerbating their water insecurity.

Augmenting supply sources will, however, not be sufficient to address this. We estimate that even a desalination project expanding municipal water supply by over 50%—while essential to alleviate overall water scarcity—would only reduce Jordan’s dependence on tanker water by 20%. In order to reduce the demand for tanker water, Jordan needs to ensure that its scarce water resources are distributed equitably. This requires reducing pipe leakages and intermittencies to reach those who currently rely on tanker water.

The second policy implication is that measures to regulate TWMs’ groundwater abstractions or emissions should account for their vital role for household water security. Jordan’s current policy is to close unlicensed wells—and this approach has been beneficial in reducing agricultural groundwater withdrawals. Applying it to TWMs, however, turns out to be detrimental to household water access. Legalizing tanker wells and ensuring—or even supporting—unencumbered deliveries to households could avoid this outcome. At the same time, Jordan’s existing tanker registration system offers the promise of mitigating additional negative impacts by covering the majority of water deliveries that supply businesses.

Meeting United Nations Sustainable Development Goal 6 is a challenge that is brought into sharp relief by the emergence of informal and illegal TWMs in many cities worldwide. These informal structures are a clear sign that public supply systems are failing to deliver sufficient water for all.

But there is another layer to the policy story. The water supplied by informal TWMs serves an important function—namely, enhancing the water access of underserved households. Recognizing this critical role of tanker water provision is essential to design measures to improve the water security of nearly one billion urban residents across the globe facing water supply stress and intermittency.