Water-Carrying Journeys and the Limits of Walking Economy Load Partitioning, Bodily Effort and Household Obligation

Abstract

Water collection joins loaded locomotion to repeated journeys, container handling and household obligations. This study asks when reducing water mass per journey changes the energy required to deliver a fixed quantity, and how household relations affect the interpretation of that comparison. Controlled carrying studies give differing results across populations and protocols; ethnographic and household research shows that access, authority and work allocation shape exposure. For one container, route and carrying method, an exact calculation retains the final partial load. Under proportional additional walking cost and constant trip overhead, smaller loads increase total energy only when they require more journeys; otherwise energy is unchanged. With nonlinear costs, energetic benefit requires the reduction in load-related expenditure to exceed additional trip overhead. A dimensionless sensitivity analysis illustrates that condition without fitting physiological parameters. A convex-cost extension distinguishes the chosen loading schedule from container capacity. Comparisons between containers require configuration-specific costs. The anthropological interpretation links these conditions to source permissions, kinship obligations, learned carrying practices and substitution between collectors. Energy, peak load, symptoms and water adequacy remain separate outcomes. Complete collection cycles and person-specific work allocation are therefore required to assess the bodily consequences of changing a carrying practice or water supply.