3.1.1. Average Daily Rainfall and Variability

There were 15 rainfall events in SES1 and 31 events in SES2; the difference in events was significant between the two seasons. This situation involves considerable risks associated with rainfed agriculture for this semiarid area, showing that strategies are required that can absorb these wide variations that occur within a 1500 ha field. The daily intraseasonal average spatial rainfall per event variability (ASREV) was significantly different in both seasons, similar to the interseasonal average spatial distribution of rainfall per rain gauge (Table 1). Generally, for most rain gauge stations, higher ASREVs were recorded during SES2 than SES1 (Figure 4).

In SES1, the probability that the rainfall covered the entire village (P100) was zero, whereas the probability of at least half the village (P50) being covered by rainfall was 42% (Table 2). No rainy days were observed for the entire village in SES1. In SES2, the probability of rain for the entire village was more than 40%, whereas the chance for at least half the village (P50) being rained on during one event was 87% (Table 2). These results show that for every 10 rainfall events, at least four events would cover the entire village and approximately nine events would cover at least half the village.


**Table 1.** Analysis of average spatial rainfall (mm) per event within and between seasons.

Note: CV is the coefficient of variation. Statistically significant at 0.05 level is denoted by a star (\*). The average values were calculated by averaging the daily rainfall (mm) for all events in a season to a single value per rain gauge, and then the variations among rainfall averages (mm) for all 38 rain gauges were tested.

**Figure 4.** Average rainfall amounts per event for SES1 and SES2. **Table 2.** Probabilities of daily rainfall coverage.


Note: The P100 and P50 values were calculated using daily rainfall data from 38 stations. P100 is a probability that for each rainfall event, all 38 rain gauges would record daily rainfall. P50 is a probability that for each rainfall event, at least half of the 38 rain gauges recorded daily rainfall. The values were obtained by dividing the maximum possible number of events in a season recorded in any rain gauge out of 38 total gauges by the minimum possible number of events at that gauge.

From the daily rainfall amounts in SES1, the calculated CV was higher (39.6–435.38%) than the seasonal rainfall (14.5%). For SES2, the daily rainfall CVs were between 12.62 and 329.67%, while the seasonal total rainfall was 10.18%, which indicates the significant daily rainfall variability compared to seasonal variability. Figure 5 shows that the daily rainfall in SES1 and SES2 was not normally distributed during many events.

We observed points far outside of the boxes (Figure 5), indicating unusually lower or high rainfall values within the same events, again indicating high spatial variability. However, SES1 shows higher unusual variability than SES2.

Both scenarios, SES1 and SES2, explain the risk of averaging the spatial rainfall per event for fields. We observed significant variations in the gauge station rainfall recorded for all events, and these variations accumulated over the entire season. Consequently, some locations had accumulated deficits resulting in severe shortages in the rainfall amount required to support crop growth, and hence, posing a high risk to crop production. In this study, we found that the accumulated seasonal rainfall amounts recorded over the entire field were significantly different among rain gauges (Table 1). The SES1 rainfall onset varied significantly over five different dates: 14 December 2016; 2 January 2017;

8 January 2017; 15 January 2017; and 30 January 2017. The cessation dates did not vary much as most of the plots (87%) received the least rainfall simultaneously. In contrast, in SES2, we observed that all rain gauges in the field recorded the same rainfall onset and cessation dates, although the rainfall amounts on particular dates varied significantly among gauges (*p* < 0.05).

**Figure 5.** Distribution of daily rainfall (mm) in (**a**) SES1 and (**b**) SES2.
