Page 144 - AJWEP-22-5

Messel, et al.

the year, discourages agricultural practices and reduces long-term mean annual rainfall of 1164 mm indicates
crop production across the region. Variability in the low overall inter-annual variability (CV: 6.94%) over
[57]
onset and cessation of rainfall affects the length of the 124 years, suggesting a generally stable annual water
growing period, as well as planting and harvesting income historically. However, this masks critical
times. This uncertainty in the cropping calendar has a seasonal and monthly shifts.
direct impact on agricultural production. [52] The pronounced seasonality, with summer (Kiremt)
As shown in Figure 3, the regression coefficients rainfall contributing 67% of the annual total, underscores
illustrated downward rainfall trends with rates of the region’s dependence on this single rainy season for
−0.343, −0.015, −0.005, and −0.404 mm/year for agricultural productivity. The statistically significant
the annual, winter, spring, and summer scales, decrease in summer rainfall, evidenced by a Sen’s
respectively, as well as a declining decadal rainfall trend slope of −0.335 mm/year (p=0.011) and a regression
(≈−2.845 mm/decade). In this case, the summer rainfall coefficient indicating a decline of −0.404 mm/year, is a
exhibits a significant downward trend. However, in major concern. This reduction during the primary crop-
autumn, the regression coefficient displays a non- growing season can lead to moisture stress, reduced crop
significant upward trend at a rate of 0.082 mm/year. yields, and increased food insecurity, consistent with
The decrease in summer rainfall (≈−0.404 mm/year) findings by Deressa et al., who noted that Ethiopian
[59]
suggests the prevalence of potential challenges in agriculture is highly sensitive to rainfall variability.
sustaining rain-fed agriculture and replenishing water The significant declining trend in August rainfall (Sen’s
resources during the main crop-growing season. On slope: −0.225; p=0.002), a peak rainfall month, further
the other hand, the non-significant increasing trend in exacerbates this vulnerability. For instance, staple crops,
autumn (0.082 mm/year) affected the crop harvesting such as teff and maize, are crucial for local livelihoods,
conditions. Overall, the reduction in rainfall during but they are highly dependent on consistent Kiremt
summer and spring could lead to lower crop yields and rains. Hence, decreased rainfall can delay planting,
reduced agricultural productivity, affecting livelihoods stunt growth, and diminish harvest volumes. [60]
in rain-dependent farming systems. A declining trend Conversely, the significant increase in November
in annual and seasonal rainfall stresses the need for rainfall (Sen’s slope: 0.045; p=0.04), while seemingly
improved water harvesting, conservation, and irrigation minor, occurs during the harvesting period for many
systems to adapt to reduced water availability. Similarly, crops in the northwestern highlands. Increased moisture
Wakjira et al. reported that the amount of rainfall at this time can lead to post-harvest losses due to rotting,
[58]
received and its seasonal distribution in the Lake Tana spoilage, and difficulties in drying grains, as highlighted
sub-basin significantly affect its agricultural activity, by Wossen et al. in similar Ethiopian contexts. The
[61]
natural vegetation, and regional humidity. high CV (49.9%) in winter rainfall (Bega), though
In a study by Mekonen and Berlie in North Wollo, contributing little to annual totals (2%), indicates
[10]
Northeast Ethiopia, regression coefficients exhibited unpredictability that can affect dry season cultivation or
successive decreasing trends at rates of −0.432, −0.335, perennial crops.
and −0.595 mm/year for summer, spring, and annual
rainfall, respectively, and −6.537 mm/decade rainfall. 3.1.2. Temporal variability and trends in air temperature
Similarly, Shekuru et al. reported that the regression The mean monthly minimum, maximum, average,
[49]
coefficients for annual, summer, and spring rainfall and decadal air temperature data from 1901 to 2022
exhibited decreasing trends at rates of 3.104, 1.707, were assessed to examine the temporal variability
and 1.431 mm/year, respectively, in the North Shewa and trends in air temperature (Table 3 and Figure 4).
Zone, Central Ethiopia. Wagesho et al. reported a Accordingly, the minimum air temperature of the study
[51]
significant downward trend in summer rainfall in the area (Lake Tana sub-basin) was found to be 7.99°C,
Tekeze River basin in northern Ethiopia. Conversely, with a maximum air temperature of 34.10°C and an
Suryabhagavan and Esayas et al. identified annual average air temperature of 21.17°C (Table 3).
[57]
[56]
statistically significant and non-significant rainfall The regression coefficients for the minimum, annual
trends in the Wolaita Zone in southern Ethiopia and average, and maximum air temperatures tended to
Ethiopia, respectively. increase at rates of 0.011, 0.008, and 0.010°C/year,
The observed temporal variability in rainfall within respectively (Figure 4). The decadal air temperature
the Lake Tana Basin carries significant implications for regression coefficient results revealed that the average,
its predominantly rain-fed agricultural systems. The maximum, and minimum air temperatures experienced

Volume 22 Issue 5 (2025) 138 doi: 10.36922/AJWEP025190142