Improvised Water Procurement in Wilderness Medicine: A Comparative Review of Yield, Energy Cost, and Field Suitability

Introduction: Access to potable water remains a fundamental need in wilderness and disaster medicine. Improvised hydration techniques such as solar stills, transpiration bags, and rain catchment are widely taught but poorly compared. This review evaluates six low resource water procurement methods for survival relevance. Methods: A structured narrative review was conducted across PubMed, Google Scholar, and grey literature sources from January 1990 to March 2025. Included studies reported water yield, labor time, disinfection potential, or energy cost. A modified Newcastle Ottawa Scale assessed study quality (max=8). Comparative energy return on hydration (EROH) was calculated using MET estimates. Results: Twenty seven studies (17 field, 10 lab) from 10 countries were included (NOS median 5, IQR 4-6). Rain catchment yielded 5-10L/event with minimal labor and no energy cost. Direct filtration produced >10L/day when surface water was available. Boiling achieved complete pathogen removal but required fuel and time. Solar stills produced <0.6L/day and demanded 375-500kcal per build. Dew and transpiration methods yielded <1L/day and required favorable humidity or sunlight. Solar stills were the least energy-efficient method. Table 1 summarizes comparative metrics; Figure 2 presents a decision-support algorithm. Conclusion: Solar stills, though historically emphasized in survival curricula, offer poor yield and an unfavorable energy profile. Modern tools like filters, catchment tarps, and chemical disinfection should be prioritized in both practice and training. Wilderness educators and responders should realign survival instruction with evidence-based hydration strategies.