International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 1 Water Requirement of Rice in Different Agro-Potential Zones Based on Aridity Indices by Using Geographic Information System Sahrish Anwar 1 and Mr. Muhammad Amin 2 1Institute of Geo-Information & Earth Observation, Arid Agriculture University Rawalpindi, Pakistan 2Faculty of Institute of Geo-Information & Earth Observation, Arid Agriculture University Rawalpindi, Pakistan Abstract: Aridity indices are widely used as an indicator of moisture availability for crop's growth. Our main objective is to determine spatial variability of aridity in Punjab, Pakistan by using different aridity indices to calculate water requirement for Rice. Climate data of eighteen weather stations in all over Punjab were collected for 25 years (1991-2016). Reference evapotranspiration (ETo) was calculated by using Modified Penman Monteith method. Annual rainfall and annual ETo was interpolated by using Inverse distance weighted method in Arc GIS 10.3 software. Interpolated data were validated by Geostatistical analysis, presented results with 99 % accuracy and Root mean square error was -0.00024. All aridity indices were calculated by using Raster calculations and mapped in GIS environment. Agro-potential zone maps based on aridity indices were developed by using Geographic Information System (GIS). Daily and monthly water requirement for Rice crop in all zones were calculated by multiplying ETo with Crop factor (Kc) values. Monthly water requirements for rice in Zone1, 2, 3, 4, 5, 6 were 816, 857, 798, 772, 770, 642 mm respectively. Optimum Seasonal water requirement for rice was 887 mm. This study will be helpful in predicting moisture availability and water need for Rice in all zones for farmers, field activity planners and policy makers. Keywords- Reference evapotranspiration, Geographic information system, Aridity indices, Agro-potential zones, Water requirement of rice 1. INTRODUCTION Rice (Oryza sateva ) is one of the important cereal crops in Pakistan (Timsina and Connor, 2001). It is grown in MayJune and harvested in October-November (Aselmann and Crutzen, 1989). Aridity is the major environmental constraint in sustainable agriculture (Haider and Adnan, 2014). About 70 to 75 % area of Pakistan consists on arid and semi-arid climatic (Chaudhry and Rasul, 2004). Twothird part of Punjab receives most of rainfall in summer season (Ahmad et al., 2015). Rice is a tropical plant, requires about average temperature of 30°C to maximum 45°C temperature and 45 to 50 inches rainfall with 15 to 16 times irrigations throughout its vegetative growth. Temperature is rising with the rate of 0.64°C annually (Afzaal et al., 2009) that's an alarming situation in country. Average annual rainfall in Punjab is about less than 10 inches (Treydte et al., 2006) which can't fulfill the requirement of water-intensive crops like rice. 1.1 Objectives of the study Our main objective of the study is to calculate different aridity indices and to delineate Agro-potential zones by using Geographic Information System. The second objective of the study is to calculate water requirements of Rice crop in all agro-potential zones. 2. MATERIALS AND METHODS 2.1 Study Area and Meteorological Data Geographical location of Punjab contributed to the possibility of Rice crop growth in arid and semi arid conditions by utilizing water for irrigation. Figure1. Map showing Geographical extent of study area It lies between 31.17° N latitudinal and 72.70° E longitudinal extent of 31.17° N and 72.70° E. Its total area is about 205,34400 hectares. Overall it falls in arid and semiarid type of climate. Maximum and minimum annual temperature of Punjab varies between 27°C to 32°C and 15°C to 19.5°C. Average annual rainfall ranges between 39 inches in upper part to 10 inches in southern districts. Relative humidity fluctuates from 50% to 63% in all over Punjab. Wind speed varies from north to south. Sunshine International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 2 hours are long in summer and short in winter. Meteorological data of 18 weather stations were acquired from Punjab meteorological department (PMD). Figure2. Methodology chart of study area 2.2 Reference Evapotranspiration (ETo) Modified Penman Monteith method is a widely used method by world renowned researchers for calculating reference evapotranspiration. It gives best results in arid and semi-arid type of environment (Rasul and Mahmood, 2009). Assessment of ETo by using climatic parameters (18 weather stations) of rainfall (mm), maximum and minimum temperature (°C), relative humidity (%), wind speed (km/day), sunshine (hours) was done by using CropWAT 8.0 software It is a software based on FAO (Food and Agricultural Organization) computation method of ETo (Piticar et al., 2016). Reference Et was calculated by using equation used by (Allen et al., 1998). (1) Where, ETo is the reference evapotranspiration (mm/day); Rn means net radiation at the crop surface (MJ/m 2 /day); G is the soil heat flux density (MJ/m 2 /day); T is the mean daily air temperature at 2 m height (°C); u2 means wind speed at 2 m height (m/s); es is the saturation vapour pressure (kPa) ; ea is the actual vapour pressure (kPa); es ea means saturation vapour pressure deficit (kPa); ∆ stands for slope vapour pressure curve (kPa/°C) and γ is the psychrometric constant (kPa/°C). 2.3 Interpolation of Meteorological Data Inverse distance weighted method was used to interpolate climatic normals by using IDW spatial analyst tool in Arc GIS 10.3 software. This method creates a raster surface characterize by similar extent of cells (Childs, 2004) and widely used for climatic parameters. Interpolated data was tested by using Geo-statistical analysis and results presented with 99% accuracy and Root mean square error was -0.00024. 2.4 Aridity Indices UNESCO Aridity Index A method of aridity computing is based on ratio of precipitation to reference evapotranspiration proposed by United Nations Educational Scientific and Cultural Organization (1979) and It was calculated by using a very simple equation used by (Dixon et al., 2013). AI = P/ETo (2) Where, AI stands for Aridity index; P is the precipitation (mm) ETo is the reference evapotranspiration (mm) Table2. Scaling of UNESCO Aridity Index Climate scaling AI values Zone ID Hyper Arid < 0.03 1 Arid 0.03-0.2 2 Semi-arid 0.2-0.5 3 Wet Sub-humid 0.5-0.65 4 Humid >0.65 5 De-Martonne's Aridity Index This aridity index was anticipated to distribute areas of different moisture characteristics. It was calculated by using equation presented by (de Martonne, 1926). AI= [P/ (T+10) +12p/ (t+10)]/2 (3) Where, P stands for average annual rainfall in mm; T = mean annual temperature (°C); p= rainfall of the driest month in mm t = the temperature of the driest month (°C) Table1. Scaling of De Martonne's Index Climate scaling AI values Zone ID Arid < 5 1 Semi-arid 5-12 2 Dry Sub-humid 12-20 3 International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 3 Wet Sub-humid 20-30 4 Humid 30-60 5 Very Humid >60 6 Erinc Aridity Index It is simple aridity index calculated by using very simple parameters. Its scaling limits are same like Thornthwaite's moisture index but parameters are simple. Following equation was adopted by (Erinç, 1996) used for calculating arid classification of study area. Im = P/ Tmax (4) Where, Im stands for Aridity index; P is the annual precipitation (mm) and Tmax is the maximum annual temperature (°C). Table3. Scaling of Erinc Index Climate scaling Im values Zone ID Hyper Arid < 8 1 Arid 8-15 2 Semi-arid 15-23 3 Wet Sub-humid 23-40 4 Humid 40-55 5 Very Humid >55 6 2.5 Water Requirement of Rice After calculation of ETo, Kc values were derived from (available literature of FAO). Crop Et was calculated by using equation adopted by (Allen et al., 1998). ETc/ CWR = ETo * Kc (5) Where, CWR = crop water requirement ETo= reference evapotranspiration (mm) Kc= crop factor 3. RESULTS AND DISCUSSION 3.1 Distribution of Aridity Indices Firstly ETo was calculated by using Eq. (1) in CropWAt 8.0 software. Interpolation maps of Climatic variable were prepared in GIS environment. Further, Aridity indices were calculated by using Eq. (2), (3) and (4) in Map Algebra (Raster calculations) and mapped in Arc GIS 10.3 software. Geographic information system was used to mark the limits of arid zones. Figure3. Arid zones based on UNESCO aridity index Figure4. Arid zones based on Martonne's aridity index Figure4. Arid zones based on Erinc aridity index International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 4 Figure5. Agro-potential zones based on all aridity indices About six Agro-potential zones having homogenous moisture characteristics were delineated and marked to calculate water requirements of Rice in all zones. Fig.5. Showing suitable zones having same agrocharacteristics. Rice is cultivated almost in all agro-potential zones of Punjab from minor to higher level. Cultivation of rice is critical in zone-1 due to hyperarid climatic conditions, so it is cultivated on small scale here with more irrigations. In Zone 2 and 3, supplement irrigations are required due to hot and arid conditions. Zone 4 is very ideal for rice cultivation due to available soil moisture, especially Sialkot, Narowal, Gujranwala, Gujrat and Hafizabad districts. Because this zone receives more monsoon rainfall in summer as compared to others. Rice is grown here with slight irrigations. In, Zone 5 and 6 varieties of rice, can be grown in such type of climate are cultivated at very small scale. 3.2 Daily and Monthly Water Requirements Daily water requirements (mm/day) for Rice crop in all agropotential zones were calculated by using Eq. (5). And monthly water requirements were calculated as mean over thirty days. Table4. Daily water requirements of Rice in all agro-potential zones As Table 4. Shows daily water requirement is calculated for every 15 th date of the months in millimeters. CWR for rice is high in the zone 1, 2 and 3 in the months of June, July and August. As Table.5.shows supplemented irrigations are required in zone 1 and 2 as CWR varies from 39.9 mm in Nov to 165 mm in July. CWR is high in the months of May, June, July and August due to hot temperature and less rainfall. Even that July and August are the rainiest months in Punjab but due to long sunshine period evaporation becomes high. Seasonal requirement of Rice is 887 mm/year. MONTH S Water requirements of Rice (mm/day) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Date May 4.02 4.01 3.78 3.91 3.79 3.69 15-May-2016 Jun 4.67 4.97 4.83 4.60 4.82 4.30 15-June-2016 July 5.30 5.50 6.16 4.65 4.90 3.96 15-July-2016 Aug 5.07 5.19 4.80 5.01 4.86 3.55 15-Aug-2016 Sep 4.10 5.21 3.52 3.92 3.80 2.96 15-Sep-2016 Oct 2.66 2.37 2.29 2.47 2.45 1.95 15-Oct-2016 Nov 1.37 1.33 1.21 1.18 1.05 0.98 15-Nov-2016 International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 5 Table5. Monthly water requirements in all Agro-potential zones Figure6. Optimum CWR of Rice Recent study showed slight shift of aridity zones from the study presented by (Haider and Adnan, 2014). The uniqueness of the study to add water requirements of Rice crop in these zones delineated from aridity indices. Figure7. Statistical relationship of Kc and CWR Strong statistical relationship R2= 0.88 of Kc with water requirement shows water requirement increase at its different stages of growth. Conclusion Geographic information system is a best technology for delineating and mapping of spatial variability of aridity over Punjab. ETo is climatic parameter helpful in determining water requirement of crops in arid and semi-arid regions. Aridity indices are best indicator for availability of soil moisture and agro-potential zones based on these indices are helpful in determining variations in water requirement of rice in all zones. This study will be helpful for farmers and field activity planners in irrigation scheduling for rice in all zones at its different stages of growth. Further studies should be occurred by using satellite based moisture indices for other crop. 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MONTH S Water requirements of Rice (mm/month) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Optimum CWR (mm) May 120.6 120.3 113.4 117.3 113.7 110.7 120.6 Jun 140.1 149.1 144.9 138 144.6 129 149.1 July 159 165 184.8 139.5 147 118.8 184.4 Aug 152.1 155.7 144 150.3 145.8 106.5 155.7 Sep 123 156.3 105.6 117.6 114 88.8 156.3 Oct 79.8 71.1 68.7 74.1 73.5 58.5 79.8 Nov 41.1 39.9 36.3 35.4 31.5 29.4 41.1 Annual/ Total 815.7 857.4 797.7 772.2 770.1 641.7 887 International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 2 Issue 10, October – 2018, Pages:40-45 http://www.ijeais.org/ijaar 6 [4] Aselmann, I., and Crutzen, P. (1989). Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions. Journal of Atmospheric chemistry 8, 307-358. [5] Chaudhry, Q., and Rasul, G. (2004). Agroclimatic classification of Pakistan. Science Vision 9, 59-66. [6] Childs, C. (2004). 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