Exploring the Modifiable Areal Unit Problem in Spatial Water Assessments: A Case of Water Shortage in Monsoon Asia

Abstract

Water shortage (availability per capita) is a key indicator of vulnerability to water scarcity. Spatial datasets enable the assessment of water shortage on multiple scales. The use of river basins and subbasins as analysis and management units is currently commonplace. An important but less acknowledged fact is that spatial assessments are strongly influenced by the choice of the unit of analysis due to the Modifiable Areal Unit Problem (MAUP). Climate conditions, agricultural activities, and access to groundwater also influence water availability and demand. In this study, a total of 21 different criteria were used to define areal units of analysis, i.e., zonings, for which water shortage was calculated. Focusing on Monsoon Asia, where water scarcity is a pressing problem, we found that zoning had a considerable impact, resulting in up to three-fold differences in the population under high water shortage (<1000 m 3 /cap/year), ranging from 782 million to 2.11 billion. In most zonings, however, the Indus and Yellow River Basins and northwest parts of India and China are under high water shortage. The study indicates that a multizonal and multiscale analysis is needed to minimize skewed or even misleading information that might be produced when using only one zoning.

Transferable Principles for Managing the Nexus: Lessons from Historical Global Water Modelling of Central Asia

“…Other units of analysis may yield some variation in quantitative results [32]. FPUs are a hydro-politically relevant scale of analysis [40], and the conclusions drawn with this unit of analysis were found to be consistent with existing literature about Central Asia.…”

“…Global water models, such as in the Water and Global Change (WATCH) project [29,30], provide widely applicable datasets for water availability and multi-sectorial water consumption. Their growing maturity, particularly in estimation of water use (e.g., [31]), has led to broad application across many scales (e.g., [4,5,[26][27][28]32]). Simultaneously, literature on global change, socio-ecological systems, and resilience has developed descriptive and normative theory regarding planetary boundaries [33] specifically, and has taken a resilience-based perspective to water sustainability [34] more generally.…”

The world’s road to water scarcity: shortage and stress in the 20th century and pathways towards sustainability

“…Calculating indicators at seasonal1157 or annual scale1858 would allow investigation of how shortage and stress occur at shorter time scales, more closely related to every-day operations rather than long-term planning. Ideally, availability would be tied to access, which would help alleviate problems related to selection of spatial scale59. Focussing on water quality6061, unsustainable water sources62, and on spatially explicit environmental flow requirements463 (the thresholds used for water stress assume global environmental flow requirements of 30%17) would explicitly identify the portion of available water that should not be used to avoid stress according to different criteria.…”

Causes and trends of water scarcity in food production

“…The choice of areal unit of analysis inherently has an effect on the results (Vör-ösmarty 2000, Salmivaara et al 2015). Particularly in global studies, such as this one, finding a single, suitable analysis unit is difficult.…”