Nourishment by means of sediments in rice paddies to reduce the subsidence in the Ebro Delta

It is predicted that 45% of the Delta Ebro´s surface will be below sea level by the end of the century. The natural sinking of the delta, otherwise known as subsidence, is the main cause of this problem, which is worsening because of the retention of sediments in upstream reservoirs and sea level rise due to climate change.

The two most important consequences of subsidence are the loss of surface in the delta -and consequently of crops- and increased water salinity.

A pilot phase has been launched by the LIFE + Ebro-Admiclim project -with the participation of IRTA´s researchers- during which sediments from the Ebro river that reach CAT´s water purification plant and remain there. are injected in the irrigation network of the Ebro Delta and in the final part of the Ebro river. The aim of this pilot test is to establish a continuous reinjection system of these sediments to compensate the negative effects of subsidence. Simultaneously, the impact of sediment addition on rice growth will be assessed.

The amount of sediments added to the study plots (0.5 Kg/m²) is comparable to what would accumulate in 100 years.

Besides assessing the need of sediment replacement, the type of fertilizers (mineral or poultry manure) used on the rice fields will also be evaluated.

The results to date (Year 1), which have to be confirmed throughout the following years, indicate that the amount of introduced sediments, mineral fertilizer, or poultry manure do not affect the rice production in the study paddies.

These results indicate that the addition of 0.5 Kg/m² of sediments in the fields through the irrigation network, regardless the type of fertilizer used, has no effect on rice production. Thus, these measures could be used to counteract subsidence in the Ebro Delta.

These data have been provided by IRTA´s and the LIFE+ Ebro-Admiclim project researcher Maite Martínez-Eixarch, during the 12^th Rice Technical Workshop held last February 10 in the Ebro Delta.

The following link provides further information about the LIFE + Ebro-Admiclim project: http://www.lifeebroadmiclim.eu/