Evaluation of Climatic Variables and Water Requirements of Rice Cultivation, and Their Influence on Irrigation Water Availability Using the CROPWAT 8.0 Model: Case Study of the M’Bahiakro Irrigated Perimeter (Central-Eastern Côte d’Ivoire)

Abstract

This study analyzes the impact of climate variability on irrigation water requirements for rice cultivation in M’Bahiakro, located in the Central-Eastern region of Côte d’Ivoire. The dataset includes rainfall (1944-2016), annual temperature records (1964-2015), and flow data from the N’Zi River (1960-2004). The analyses were conducted using the Nicholson rainfall index, the Hanning filter for seasonal smoothing, as well as the Pettitt and Lee & Heghinian tests for the detection of structural breaks, defined as abrupt changes in the statistical properties of a time series such as the mean, variance, or trend. The results indicate that some preliminary signals suggest the onset of a shift as early as 1968, whereas the Pettitt test identifies 1973 as the most statistically significant breakpoint. Consequently, 1973 was selected as the main reference for delineating the climatic periods. Three phases were thus defined: a wet period (1944-1972), a transition phase (1973-1996), and a dry period (1997-2016). The mean annual temperature increased by approximately 0.5˚C, confirming a progressive warming trend. From a hydrological perspective, the mean discharge of the N’Zi River decreased by nearly 47%, from 55.57 m 3 /s (1960-1972) to 29.63 m 3 /s (1973-2004), highlighting the strong sensitivity of the basin to climate variability. Furthermore, irrigation water requirements for rice increased by about 22% between 2009 and 2016 as a result of rising temperatures and increasing irregularity in rainfall patterns. Overall, these findings underscore the growing vulnerability of the irrigated perimeter to climate variability and emphasize the need for integrated water management, improved irrigation efficiency, and the adoption of sustainable adaptation practices.