Long-Term Hydrological Regime Monitoring of a Mediterranean Agro-Ecological Wetland Using Landsat Imagery: Correlation with the Water Renewal Rate of a Shallow Lake

Abstract

The Natural Park of Albufera (Valencia, Spain) is one of the Spanish Mediterranean wetlands where rice is cultivated intensively. The hydrology of the Albufera Lake, located in the center, combines natural contributions with complex human management. The aim of our study was to develop a new methodology to accurately detect the volume of flood water in complex natural environments which experience significant seasonal changes due to climate and agriculture. The study included 132 Landsat images, covering a 15-year period. The algorithm was adjusted using the NDWI index and simultaneous measurements of water levels in the rice fields. The NDVI index was applied to monitor the cultivated area during the summer. Lake inflows and residence times were also evaluated to quantify how the hydrodynamic of the lake is conditioned by the agricultural management. The algorithm developed is confirmed as a useful ecological tool to monitor the flood cycle of the wetland, being able to detect even the lowest water levels. The flood dynamics are consistent over the fifteen years, being in line with the rice cultivation cycle. Water renewal in Albufera lake is altered with respect to that expected according to the rainfall recorded in the study area, so an improvement in the water management of the hydrological basin is required to optimize the runoff during the rainiest months.

Using a Bayesian network model to predict effects of pesticides on aquatic community endpoints in a rice field – A southern European case study

“…The study area is a coastal wetland around five kilometres south of Valencia on the Mediterranean Spanish coast, with an area of about 210 km 2 (Figure 1). The Natural Park has ecological relevance as it is a nesting and transfer point for approximately 250 species of migrating birds and mentioned in as a special protection area by Birds Directive (Directive 2009/147/EC), listed as European habitat in Natura 2000, and Ramsar Convention of wetlands (Calvo et al, 2021; GV, 2020; Vera-Herrera et al, 2021). Within its bound, 34% of Spanish rice is produced (Canet et al, 2003) as 73% of the wetland is dedicated to rice cultivation (Vera-Herrera et al, 2021).…”

“…The study area is a coastal wetland around five kilometres south of Valencia on the Mediterranean Spanish coast, with an area of about 210 km 2 (Figure 1). (Calvo et al, 2021;GV, 2020;Vera-Herrera et al, 2021). Within its bound, 34% of Spanish rice is produced (Canet et al, 2003) as 73% of the wetland is dedicated to rice cultivation (Vera-Herrera et al, 2021).…”

“…This is of special concern in the Albufera Natural Park (Valencia, Spain) a lake enclosed by rice fields, known for its diversity in bird and fish species (Soria, 2006). In this area, the rice production and other anthropogenic stressors already had a negative impact on lake’s water quality and ecosystem health throughout the last century (Calvo et al, 2021; Vera-Herrera et al, 2021). Realistic assessment of risk posed by these expected stressors is therefore crucial for the future ecological sustainability of the Albufera National Park.…”

How Agriculture, Connectivity and Water Management Can Affect Water Quality of a Mediterranean Coastal Wetland

“…The lake's hydrological cycle has two periods of low water renewal from November to December and from April to September during rice sowing and growing. The higher lake water renovation takes place between January and March after the emptying of the paddy fields and by September-October after harvesting [34,51,54]. The lake water level is regulated by three artificial outlet canals, which flow into the Mediterranean Sea [51].…”

“…In addition, recently new tools and methodologies have emerged for the environmental assessment of wetlands, such as remote sensing [30], which can evaluate the state of water bodies at spatial and temporal levels at different resolutions, and algorithms have been developed to measure limnological parameters [31][32][33][34]. Moreover, geographic information systems (GIS) have allowed new approaches in recent years different environmental compartments incorporating into environmental studies (known as landscape functional areas, LFAs) [35], as well as the hydrological connectivity between zones.…”