The Jordanian water sector faces simultaneous challenges from a per capita water availability of less than a third of the absolute scarcity threshold of 500 CM per capita per year and a rapidly growing population, especially due to the Syrian refugee crisis. These challenges are often seen as a call for supply enhancements. Since most of the available supply enhancement options are, however, non-renewable, any long-term solution also needs to include water demand management (WDM) measures that lead to more sustainable consumption patterns. Such long-term solutions are analyzed by the Stanford-led G8 Belmont Forum project "Integrated Analysis of Freshwater Resources Sustainability in Jordan" (Jordan Water Project, JWP). In order to consider the relevant geophysical and socio-economic scenarios, the project develops a coupled hydrological and agent-based model. This model will be used to explore various institutional and policy interventions aiming at a sustainable use of freshwater resources and to anticipate the distribution of burdens across society.
The part of this integrated model in focus here is the representation of household behavior in Jordan's densely populated capital Amman. Amman's piped water supply is characterized by high intermittency and hence limited suitability for drinking purposes. Amman's citizens show diverse reactions to this situation, depending on their socio-economic characteristics and location within the city. They rely on tanks of various sizes to store piped water, public and private tanker trucks, supplying additional water, and bottled drinking water. This has consequences for assessing the impacts of WDM policies, since not only changes in piped water demand patterns need to be considered, but also the demands for substitutes and their welfare effects, as well as the role of supply intermittency and storage constraints. Analyses are further complicated by the fact that part of the private tanker water supply originates from illegal water extractions and, thus, data availability is limited.
In order to assess the effects of WDM policies under Amman's water supply conditions, we have created a numerical simulation model based on the tiered supply curve approach, which was developed by Srinivasan et al. (2011) for a similar situation in Chennai, India. This approach allows for the analysis of demand quantities from various supply sources and the corresponding consumer surplus contributions in a unified framework. Data on the spatial distribution of weekly piped water supply durations and storage tank sizes, on socio-economic household characteristics, and on the availability and prices of the different supply sources is used to tailor our model to the specific situation in Amman.
The allocation of the available piped water quantity among high- and low-income households in the different districts of Amman is simulated based on their demand function, local supply duration, and storage capacity, as well as the current water tariff structure. The more expensive tanker water supply serves to cover additional demand unmet by the constrained and intermittent piped water supply. Scenario parameters allow for the analysis of WDM policy interventions, such as piped water tariff increases, and hydrological scenarios, such as decreases in the overall water availability. The model output consists of the quantities of piped and tanker water consumed by households in the different districts and income classes, as well as the consumer surplus changes under different scenarios, compared to the baseline. The model developed will later serve as a basis for the representation household water consumption in the JWP integrated model.
A baseline scenario is used to estimate the current spatial distribution of tanker water demand in Amman. This provides new insights into the spatial structure of this partially informal market. Subsequently, various WDM policy interventions are analyzed under a number of scenarios. Raising the average tanker water price, for example by increasing the enforcement of laws against illegal water extractions, imposes consumer surplus losses on all households using tanker water. In contrast, proportionately increasing all levels of the piped water tariff structure creates both winners and losers, since all tariff changes affect the distribution of the overall water quantity available via the piped water system. Even uniform reductions of supply intermittency are not found to be beneficial to all households, as they also effectively lead to redistributions of the total piped water quantity. Together, the analyses highlight the importance of disaggregating policy impacts on households spatially and by socio-economic characteristics in order to identify and possibly mitigate the burdens which potential WDM policy options impose on different parts of society.
1. Srinivasan, V., Gorelick, S. M., and Goulder, L. (2010) Sustainable urban water supply in south India: Desalination, efficiency improvement, or rainwater harvesting? Water Resources Research 46, W10504. doi: 10.1029/2009WR008698