## 2 Materials and Methods
### Data Collection and Processing  
The investigated data of farm's contents and farmer's activities were obtained from the Saudi Irrigation Organization (formerly Hassa Irrigation and Drainage Authority, HIDA), Al-Ahsa, KSA (accessed on 11 November 2020). Throughout the course of data collection, many criteria were taken into consideration, namely: geographical location (i.e., GPS), irrigation water sources (i.e., underground, tertiary treated wastewater, or mixed), farm cultivated areas (m\({}^{2}\)), irrigation methods (i.e., channel, ditches, pipes, etc.), and crop types. Collected data of farms and farmers were then divided into different categories according to specific criteria throughout the major three subareas over the oasis, which were Jlejilah, Al-Mansourah, and Al-Harah, and then over 25,400 farms were spotted and covered within the farms' network, 6281, 5919, and 3259 farms, respectively. The farms allocated to the subareas were carefully selected to the current study, as they are in line with its objectives.  
To set a suitable size for the collected samples that represent all farms with common features all over the oasis, this study applied the proportional stratified random sampling approach constructed by [PERSON] and [PERSON] [43], who belong to the research division of the National Education Association. In this technique, the formula used to determine the sample size of a set of data was as follows  
\[S=\frac{X^{2}NP(1-P)}{d^{2}(N-1)}+X^{2}P(1-P) \tag{1}\]  
where  
\(S\) = required sample size.  
\(X^{2}\) = the table value of chi-square for 1 degree of freedom at the desired confidence level (3.841).  
\(N\) = the population size.  
\(P\) = the population proportion being assumed to be 0.50, as it would provide the maximum sample size.  
\(d\) = the degree of accuracy expressed as a proportion (0.05).  
Making use of the proportional stratified random sampling approach [43], the collected number of farms was downsized into 288 representative farms. The applied criteria included difference in oasis section's orientation (i.e., Jlejilah, Al-Mansourah, and Al-Harah), difference in cultivated areas (i.e., small, medium, and large), differences in type of irrigation and irrigation source, and farm's agricultural products (i.e., types, cultivars variety, and quantity).  
It is worth stating that there have been more than 40 different cultivars of date fruit observed from the collected data from the Al-Ahsa farms. Hence, the 3 most preferably cultivated cultivars of date fruits were selected by nominating the most frequently cultivated ones in the oasis. Thus, the applied frequency analysis of the collected 25,400 farms' data revealed that \"Khlas\", \"Ruziz\", and \"Shishi\" cultivars were the most cultivated in the oasis (in terms of number of trees/farm), with frequency percentages of 65%, 16%, and 4%, respectively. These 3 cultivars were, hence, applied to depict and map the density (i.e., number of trees per farm) and spatial distributions of date palm trees in the Al-Ahsa oasis.  
Cultivar's specific area and distribution were also delineated by identifying farms with an entirely growing sole cultivar, then dividing the farm cultivated area by the number of sole cultivar trees to produce the area of a single tree in m\({}^{2}\). Hence, for the farms that had the same criteria, the average total area of the specified cultivar was then calculated. Finally, the spatial distribution of cultivated areas, total palm, and selected cultivars of the representative farms was mapped utilizing a spatial interpolation (inverse distance weight-IDW) technique in the ArcGIS software program's environment.