Novel Quantification of Long-Term Hydrological and Landscape Spatiotemporal Dynamics of Coupled Natural Human Systems: The Case Study of the Tempisque-Palo Verde National Park Coastal Wetland, Costa Ric

The 5,412 km2 Tempisque watershed in NW Costa Rica was significantly transformed in the late 1970's through the addition of an inter-basin water transfer for hydropower generation and a large irrigation district. These changes ultimately impacted the Palo Verde National Park (PVNP) coastal wetland designated as a Ramsar site of international importance. This dissertation addresses the importance of advancing the knowledge of the governing processes, interactions, and long-term spatiotemporal dynamics of coupled human and natural systems (CNHs) such as the Tempisque watershed and PVNP to inform management strategies that reconcile the human and natural needs. We compiled a novel long-term public database of hydrological, meteorological, and land cover data for the watershed and the PVNP wetland. We showed that the combination of the recent open-access data policy for pre-processed satellite archives such as Landsat and MODIS, the new cloud-base Google Earth Engine (GEE) platform, and affordable field monitoring sensors generates unprecedented opportunities to readily build custom and high-frequency long-term time series data to document changing ecosystem dynamics in CNHs studies. To examine land cover history, we reconstructed aggregated Normalized Difference Vegetation Index (NDVI) monthly time series from Landsat and MODIS imagery with GEE and detected an increased vegetation greening in the entire watershed and wetland. We used our ground monitored water level data to define a spectral index for wetland hydric status detection, and used it to reconstruct a 2000-2016 wetland hydroperiod biweekly time series from MODIS images. The outcomes allowed a novel and important insight into the PVNP wetland hydrology and its connections with the surrounding rivers and agricultural district. Finally, we hypothesized and found strong support for the theory that the detected long-term decrease in the Tempisque river discharge caused by excessive water withdrawal leads to an increased flooding in the wetland. River discharge attenuates the tidal cycle and thereof reduces the frequency of tidal flooding. The discovery of this relationship has important implications for the PVNP wetland and many coastal systems worldwide. The results of this dissertation and recommendations for further studies are pioneering a larger research effort to untangle this CNH's complex processes and inform sustainable management.