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•New baseline strontium ratios and oxygen isotope values reported from northern Belize.•Study area: Río Bravo Conservation and Management Area, northwest Belize.•δ18O values may reveal differences in drinking water reservoirs between sites.•Isotopic data show movement was consistent into and throughout the RBCMA from the Preclassic through the Terminal Classic.•Rural areas experienced more diachronic movement than urban areas. This may be related to changing sociopolitical issues.

Much Maya research has studied water management, but very little has studied water quality. Water chemistry reflects local and regional geology, soil, and land uses. Thus, it can supply a useful link between past and contemporary environmental conditions. This research analyzes the water quality of sources near archaeological wetland sites in the Three Rivers Region, northwestern Belize to better understand Precolumbian Maya land and water use potentials and possibilities for contemporary water use at these sites. We explore quality complications for crop types, including forests and orchards, as well as paleoenvironmental and modern botanical information to test hypotheses about water limits and possibilities in the region. Our evaluation of water quality also presents implications for domestic consumption of the region's waters and public health. Broad scale results for this region show chemically distinct water sources that include waters that are limited for agricultural and domestic uses, and other waters that are acceptable for these uses. We infer that near surface water chemistry in the lowland part of our study region also changed from the Preclassic into the Terminal Classic Period and beyond due to sea level and concomitant groundwater rise, which had profound impacts on Maya land and water use that continue to the present. In sum, we review Maya Lowlands water quality and present a case study in Belize to understand better the wetland agricultural and domestic use implications influencing this tropical, karst civilization.

The Pakbeh Regional Economy Program is studying the vexing questions of economic life among the ancient Maya in northwestern Yucatan, Mexico. The region constitutes an ideal laboratory in which to investigate these questions, as it has very limited agricultural potential and fewer options for intensification than are found in the southern and central lowlands, yet many times more people lived here during the Classic period than can eke out a living today, and it has abundant evidence of market trade. Because crop yields in outfields are very low, and known intensification techniques are possibly incapable of sufficient yield enhancement, we anticipated that it would be an easy task to demonstrate that this population was dependent on imports of food and other necessities of life from beyond the region and therefore had a complex exchange economy. Twelve years later, we report on how wrong we were. We are still struggling with an evaluation of agricultural insufficiency. We explore the many and varied lines of evidence we have pursued and the confounding factors inherent in them, including problems with reconstructing ancient population size, equating contemporary and historical crop yields and farming practices, as well as ancient with modern environmental conditions, and hypothesizing potential forms of agricultural intensification, including intensive fertilization and other yield enhancement techniques, and reliance on alternative crops. The best that we can say at this juncture is that using contemporary production and consumption standards, the most conservative population estimates, and the most liberal estimates of available land in the surrounding region, we can conclude only that regional agricultural self-sufficiency remains unlikely but not proved. What initially seemed like an archaeological “no-brainer” has required us to delve into the realm of archaeological epistemology that we would like to share with our colleagues.

Abstract: What size sample is sufficient for spatially sampling ambient groundwater quality? Water quality data are only as spatially accurate as the geographic sampling strategies used to collect them. This research used sequential sampling and regression analysis to evaluate groundwater quality spatial sampling policy changes proposed by California's Department of Water Resources. Iterative or sequential sampling of a hypothetical groundwater basin's water quality produced data sets from sample sizes ranging from 2.8% to 95% coverage of available point sample sites. Contour maps based on these sample data sets were compared to an original (control), mapped hypothetical data set, to determine at which point map information content and pattern portrayal are not improved by increasing sample sizes. Comparing series of contour maps of ground water quality concentration is a common means of evaluating the geographic extent of groundwater quality change. Comparisons included visual inspection of contout maps and statistical tests on digital versions of these map files, including correlation and regression products. This research demonstrated that, down to about 15% sample site coverage, there is no difference between contour maps produced from the different sampling strategies and the contout map of the original data set.

•Study combines excavations with lidar and qualitative soil phosphorus surveys.•Linear stone features appear to demarcate ancient Maya houselots.•Mean interior area of proposed houselots is large in comparison to other regions.•Dense settlement and larger houselots may signal decreased use of outfields.•Data may indicate the existence of private land tenure during the Late Classic period.