Abstract
Abstract. Drained peatlands are one of the main sources of carbon dioxide (CO2) emissions globally. Emission reduction and, more generally, ecosystem restoration can be enhanced by raising the water table using canal or drain blocks. When restoring large areas, the number of blocks becomes limited by the available resources, which raises the following question: in which exact positions should a given number of blocks be placed in order to maximize the water table rise throughout the area? There is neither a simple nor an analytic answer. The water table response is a complex phenomenon that depends on several factors, such as the topology of the canal network, site topography, peat hydraulic properties, vegetation characteristics and meteorological conditions. We developed a new method to position the canal blocks based on the combination of a hydrological model and heuristic optimization algorithms. We simulated 3 d dry downs from a water saturated initial state for different block positions using the Boussinesq equation, and the block configurations maximizing water table rise were searched for by means of genetic algorithm and simulated annealing. We applied this approach to a large drained peatland area (931 km2) in Sumatra, Indonesia. Our solution consistently outperformed traditional block locating methods, indicating that drained peatland restoration can be made more effective at the same cost by selecting the positions of the blocks using the presented scheme.
Highlights
Peatlands occupy around 3 % of global land area but hold up to one-third (630 Pg) of all carbon (C) held in active terrestrial pools (Page et al, 2011; Page and Baird, 2016; Xu et al, 2018; Le Quéré et al, 2018; Nichols and Peteet, 2019)
After 3 dry days, the Water table depth (WTD) drops about 10 cm at the midpoint between two drains separated by 1.4 km
The behavior of the canal water level subroutine is demonstrated by comparing the CWL change in a small drained area with and without canal blocks (Fig. 6)
Summary
Peatlands occupy around 3 % of global land area but hold up to one-third (630 Pg) of all carbon (C) held in active terrestrial pools (Page et al, 2011; Page and Baird, 2016; Xu et al, 2018; Le Quéré et al, 2018; Nichols and Peteet, 2019). Even though drainagebased bioproduction can be economically viable, it has severe environmental drawbacks: it increases CO2 emissions (Ojanen et al, 2010; Jauhiainen et al, 2012), the rate of peat subsidence (Couwenberg et al, 2010; Hooijer et al, 2010; Carlson et al, 2015; Evans et al, 2019), nutrient export to water courses (Nieminen et al, 2017) and fire risk in peatlands (Usup et al, 2004; Wösten et al, 2008; Page and Hooijer, 2016). C emissions from tropical peatlands in Malaysia and Indonesia in 2015 corresponded to 1.6 % of Published by Copernicus Publications on behalf of the European Geosciences Union
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