**2.5.4 Ponding Water Index (PWI)**

The Ponding Water Index is the relation between present and the maximum desired ponding water depth for the duration being considered. It indicates the state of the water deliveries for a specific period with respect to the desired ponding water depth in the field during the crop growing season. It can be expressed as the following equation:

$$\text{PWI}\_{\text{j}} = \frac{\text{WS}\_{\text{j}} - \text{WSmax}\_{\text{j}}}{\text{WSmax}\_{\text{j}}} \tag{8}$$

Where

WSj is the measured ponding water depth on j-th day WSmaxj is the maximum desired ponding water depth on j-th day

The WSmaxj is normally varied from 2 to 10 cm during the crop growth periods. For achieving good irrigation water delivery performance and efficient water management, the PWIj is recommended to be maintained at -1.0 > PWIj ≤ 0. Ponding Water Index gives the following interpretation over periodic irrigation supply at the end of a period:

> PWIj > 0 Over supply condition PWIj = 0 Well-watered condition PWIj = (-ve) Under supply PWIj = -1.0 Critical or saturation condition.

The PWIj gives distinct scenarios whether irrigation supply could be supplied properly or not during the crop growth periods. It gives the useful information for irrigation management decisions to managers. The indicator can also quantify the amount of undersupply with respect to maximum desired ponding water depth at the field level for the week being considered.

### **2.6 ArcGIS user-interface and operation procedures**

Rice Irrigation Management Information System (RIMIS) with delivery performance assessment tool was developed for the Tanjung Karang Rice Irrigation Scheme as a userfriendly interactive system. RIMIS is an ArcGIS-VBA user-interface with many sub-modules and functions within the powerful ArcGIS environment. On activation of ArcGIS Software, the menu "RIMIS" appears directly on the Menu Bar in the ArcMap Window (Fig. 2). On clicking the Command Button, "Irrigation Delivery Performance" in Fig. 2, the Dialog Wizard for irrigation delivery performance will appear. RIMIS allows the irrigation manager to run the day-to-day operation and management activities as the season advances. The program is used to characterize the daily irrigation water allocation scenario and to

with the field water demand for a particular irrigation period. An increasing slope of the actual CRRWS curve with CRRWS = 1.0 means that irrigation supply can be slightly curtailed in the next period. On the other hand, if the slope is downwards, supply has to be

The Ponding Water Index is the relation between present and the maximum desired ponding water depth for the duration being considered. It indicates the state of the water deliveries for a specific period with respect to the desired ponding water depth in the field

WSj <sup>j</sup>

WSmax

The WSmaxj is normally varied from 2 to 10 cm during the crop growth periods. For achieving good irrigation water delivery performance and efficient water management, the PWIj is recommended to be maintained at -1.0 > PWIj ≤ 0. Ponding Water Index gives the

PWIj > 0 Over supply condition

PWIj = 0 Well-watered condition

PWIj = (-ve) Under supply

PWIj = -1.0 Critical or saturation condition. The PWIj gives distinct scenarios whether irrigation supply could be supplied properly or not during the crop growth periods. It gives the useful information for irrigation management decisions to managers. The indicator can also quantify the amount of undersupply with respect to maximum desired ponding water depth at the field level for

Rice Irrigation Management Information System (RIMIS) with delivery performance assessment tool was developed for the Tanjung Karang Rice Irrigation Scheme as a userfriendly interactive system. RIMIS is an ArcGIS-VBA user-interface with many sub-modules and functions within the powerful ArcGIS environment. On activation of ArcGIS Software, the menu "RIMIS" appears directly on the Menu Bar in the ArcMap Window (Fig. 2). On clicking the Command Button, "Irrigation Delivery Performance" in Fig. 2, the Dialog Wizard for irrigation delivery performance will appear. RIMIS allows the irrigation manager to run the day-to-day operation and management activities as the season advances. The program is used to characterize the daily irrigation water allocation scenario and to

j WSmax

<sup>−</sup> <sup>=</sup> (8)

during the crop growing season. It can be expressed as the following equation:

j

following interpretation over periodic irrigation supply at the end of a period:

PWI

WSj is the measured ponding water depth on j-th day

**2.6 ArcGIS user-interface and operation procedures** 

WSmaxj is the maximum desired ponding water depth on j-th day

increased.

Where

**2.5.4 Ponding Water Index (PWI)** 

the week being considered.

evaluate the irrigation delivery performance using the selected performance indictors as the season advances.

Fig. 2. The RIMIS Menu for the Tanjung Karang Rice Irrigation Scheme (TAKRIS) in ArcGIS

The user needs to enter the required inputs and choose the appropriate command button to view the results. Inputs can be directly fed into the dialog window by clicking on the command button "Data from Input Files" or manually (Fig. 3). All required inputs stored in Input Files are instantly retrieved into TextBoxes by each irrigation service area i.e. "ISAI: Input Daily Information (I)". Command Buttons for new irrigation delivery performance indicators, Rice Relative Water Supply (RRWS), Cumulative Rice Relative Water Supply (CRRWS) and Ponding Water Index (PWI) together with the Relative Water Supply (RWS) concept are shown in Fig. 3. Users may feed accurate information from other sources manually if available and reliable. To compute the performance indicators correctly, users should enter the actual information of rainfall and reference crop evapotranspiration on the day as they are available at the end of the irrigation day. A sub-routine was developed to compute the daily potential crop evapotranspiration as shown in Figures 4a and 4b. This sub-module allows an irrigation manager to compute the daily Reference Crop Evapotranspiration (ETo) using the Internationally recommended FAO Penman-Montieth Equation based on the available climatic information for a particular day. However studies by Hassan (2006) show that ETo calculated by the Penman-Montieth Equation gives an underestimation of ETo by 10% compared to ETo from micro-lysimeters installed in the paddy fields.

Paddy Water Management for Precision Farming of Rice 119

(a) Input Selection Dialog Wizard

(b) Input Dialog Wizard for Daily Meteorological Data

Fig. 4. Computing Daily ETo using FAO Penman-Monteith Method

The system allows for storing of all inputs and outputs into the MS Access database simply by clicking on the Command Button "Save". It has also capabilities of retrieving, editing, deleting records from database for a particular day upon selection. The Command Button "Backup" helps to keep all files as backup any time. The dialog wizard linked with the Command Button "View Inputs & Outputs" in Fig. 3 allows interactive viewing for all input and output databases. It enables to users viewing data in table and graph formats. The records of the selected table are displayed. The records from the selected Table can be viewed for a specified duration and the selected fields. The easily obtained comprehensive information allows the manager to characterize the irrigation delivery performance faster. The dialog wizard for exploring the scheme's information can also be viewed on clicking the command button "Detailed Scheme Information" in Fig. 3. This sub-module gives salient features of the scheme in the form of maps, graphs and tabular formats.


Fig. 3. Dialog Wizard for Characterizing Irrigation Delivery Performance for the Main Season
