Modeling-based performance assessment of an indigenous macro-catchment
water harvesting technique (Marab) in the Jordanian Badia
Abstract
Water resources management is fundamental for rural communities in
drylands. Water Harvesting Technologies (WHT) intercept and store the
excess rainfall (surface runoff) in soils for increased plant available
water and agricultural productivity. The so-called ‘Marab’ WHT was
initially developed by Middle Eastern agro-pastoralists that reside or
commute in semi-arid and arid rangelands. The Marab WHT is a
macro-catchment measure consisting of earth dams and stone spillways
along the contours of a lowland depression or floodplain. Dependent on
the local context (i.e. climate, soil, management, etc.) the established
Marabs show highly-variable effectiveness. This study aims at filling
the knowledge gap on the WHT’s performance in changing environments by
simulating its hydro-agrological effects for different soils and
climatic conditions using the AquaCrop model. A case study performed for
a Jordanian Marab over three seasons (2019-2022) confirms its huge
improvement potential for barley production. Through Marab-farming,
barley production reached 8.37 t ha -1 on average,
versus highly variable 0.34 t ha -1 without the WHT.
The simulation-based assessment of soil textures identified that silty
soils have the largest potential for producing up to 9.25 t ha
-1 barley, compared to 6.60 t ha -1
produced in clay soils. Assessing different climate scenarios, a slight
increase in daily average temperatures (+ 0.5°C) led to a considerable
production decline of 4-8%, while a significant reduction of
precipitation (-20%) decreased biomass production by a similar rate
(4-10%). This underlines the robustness of the ‘Marab’ WHT to rainfall
amount variation. However, simulations also highlight the sensitivity of
timing and frequency of flood events: removing the last and the first
flood event reduced biomass production by approximately 50% and 80%
respectively, while the barley fails to develop if both events were
suppressed.