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Core Ideas An innovative low‐cost open‐source Arduino‐based datalogger was developed. The datalogger was deployed for hydrologic monitoring in tropical watersheds. Arduino datalogger performance was robust after overcoming initial challenges. The system has great potential for automated continuous environmental monitoring. Continuous hydrologic monitoring is limited in many regions of the world, creating serious knowledge gaps for water resources managers and scientists. Recent advances in open‐source software and hardware technologies, such as the Arduino project, show potential for the development of low‐cost (∼$100) automated dataloggers required for continuous data collection. We developed an Arduino‐based datalogger (the Ecohydro Logger) coupled with water sensors providing digital output to establish a hydrologic monitoring network in the data‐scarce wet‐dry tropics of Guanacaste, Costa Rica. While we experienced some challenges with a first iteration of our Arduino‐based datalogger, an improved version was robust and able to capture long periods of high‐frequency stream discharge data. Integration of the monitoring program into the local community was also key to successful deployment, allowing exchange of local knowledge and support. The accessible and low‐cost nature of Arduino‐based dataloggers can provide a means to extend continuous environmental monitoring into data‐scarce regions.

Agricultural expansion and intensification is occurring in seasonally dry regions of Central America, while droughts are intensifying due to increasing water demand and climatic change. Empirical measurements of water consumption of major crops in this region are scarce but crucial to assess agricultural water use dynamics in the light of increasing regional water conflicts. We empirically quantify total crop water use (CWU) and water footprints (WFs) of rainfed upland rice (wet season) and groundwater‐irrigated melons (dry season) grown sequentially as a double cropping system, one of the major cropping systems in the seasonally dry province of Guanacaste in northwestern Costa Rica. Data for this study cover 2 years and were measured with a state‐of‐the‐art eddy covariance water and carbon flux station. Upland rice only consumed green water (CWUgreen = 383 L/m2), while melons only consumed blue water (CWUblue = 177 L/m2). Irrigation was found to be 1.5 times larger than the actual melon water consumption, with better irrigation efficiencies than reported for melon farms in Brazil but slightly inferior to farms in Spain. Melon WFblue was 79 m3/t, a much lower value than global and regional estimates reported but similar to values reported for melons produced in Brazil or Spain. Upland rice WFgreen (681 m3/t) was reported for the first time and was proven to be much lower than flood irrigated‐rice WFblue‐green. Our results demonstrated lower overall water demand for upland rice‐melon double crop compared to the two other major monocultures of the region (flood‐irrigated rice and irrigated sugar cane).

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Rainfall amounts and seasonal rainfall cycles in tropical regions are likely to shift with climate change (Magrin et al., 2014), but it remains poorly understood how this may impact streamflow and groundwater in regions with complex climate patterns, such as the seasonally dry (i.e., wet-dry) tropics of Central America. The rural agricultural communities of this region suffer from recurring droughts, water shortages, and water conflicts (

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