MODELING EARLY-SEASON CROP-GROWING ENVIRONMENT RAINFALL BASED SOIL MOISTURE STATUS AND CROP PROSPECTS Dr. M. Chakraborty

INPUTS: Daily spatial rainfall data over India (Sources: Kalpana IMSRA, NCEP/NOAA CPC daily rainfall estimation data adjusted to IMD station-wise daily rainfall data, IMD Gridded RF data) Climatic Potential Evapo-transpiration data (Source: Monthly PET data from IMD Agrimet Division, Pune) Survey of India Soil Texture Map – 1:6M Published Moisture Holding Values for each Soil Texture Class, Hydraulic Conductivities (Sources: 1. David R Maidment, Ed in Chief, Handbook of Hydrology 2. Carsel, RF and RS Parrish, Water Resource Res. 24: , TH. J. Bredero, Crop-Water Management Research – A Case Study for India) MODEL USED: DAILY SOIL MOISTURE BUDGETING (Compound Bucket Model, cm depth – Root Zone) - One-dimensional model (vertical direction) - Bunded (20 cm or more) agricultural fields. (No runoff from or to) - AET estimation from Climatic PET - Using Soil Moisture Availability, AET/PET Drying Curve, Crop Coefficients (k c ) - Percolation using Saturated and Unsaturated Hydraulic Conductivities (K s, K c ) - Ponding of water in agricultural fields (input to flood assessment) - Provision for inclusion of Crop Calendar (Spatial Layers) and corresponding Crop Coefficients (Spatial and Temporal). - Rainfall based, provision for inclusion of irrigation water. Model was calibrated using reported field measured soil moisture in top 30 cm under saturated and unsaturated conditions (percolation and ET loss) for measured moisture holding capacities of the soil and PET. OUTPUTS: Root Zone Soil Moisture (v/v), Ponded Water, Estimated Daily AET, Deep Percolation

INPUTS: PWP SM % v/v FC SM % v/v SAT SM % v/v K s mm/d n (exponent for computing unsaturated K c ) Agricultural Area Crop Specific Area Administrative Area Met-subdivision Area River Basin Area Initial SM % v/v Initial Surface Water mm Daily PET mm (from Climatic, Monthly data) Daily k c (from crop calendar, empirical models) Daily RF mm Daily Irrigation mm OUTPUTS: Daily SM % v/v Daily Surface Water / Runoff mm Daily Deep percolation (Ground water) mm Derived Outputs (Daily, Weekly etc) Drought Status Crop Sowing Suitability Kharif Rice Kharif Coarse Cereals Crop Growth Suitability Irrigation Requirement in mm Flood Risk Assessment Reservoir Inflow / River Discharge Estimation

Root Zone Layer Depth 15 to 120 cm Top 10 cm Evaporation Layer Daily Irrigation Command Area Irrigation Schedules Daily Rainfall Model Estimation (Spatially Distributed) Kalpana IMSRA, NCEP CPC RFE, IMD Gridded RF Adjusted with IMD Station measurements Daily Evaporation Climatic PET (Published values) Crop Coefficient k c (dynamic, using Crop Calendar) Soil Moisture θ T, θ RZ Soil Drying Function Ponded Water (From previous day) Daily Saturated / Unsaturated Flow θTθT θ RZ SM θ (Average value) End of Evaporation Cycle Hydraulic Conductivities K S : Saturated K C = K S (θ / θ Sat ) n : Unsaturated Uniform Mixing Soil Properties Saturation θ Sat Field Capacity θ FC PWP θ PWP K s, n Output: Daily Soil Moisture values in % v/v Daily Available Soil Moisture (ASM) in % = (θ – θ PWP ) / (θ FC – θ PWP ) x 100 Compound Single-Bucket For each Day of the Season Soil Texture Class Map (SOI 1 : 6 M scale) Published PWP, FC, Sat. Moisture Values % v/v, Hydraulic conductivities K s and n for each Texture Class. Map layer output for each parameter. Antecedent Soil Moisture Ground-water Recharge AET

Agriculture Area Mask Crop and Season-specific District Area Mask (Significant crop proportion) Valid Area Mask for RF Models For each Day of the Season Crop Area for Statistics (Crop-specific) - Population Daily ASM 7-day Moving Average of ASM ASM AVG > Thres Crop Crop Area suitable for Sowing / Transplanting Crop Calendar Function (for sowing) (Crop, Season, Area specific) CCFS (0.0 to 1.0) (Cumulative Distribution Function) Accumulate Crop Suitable Area over time True Multiply by CCFS Crop Area Sown / Transplanted Jun 15Aug Kharif Rice (Winter) Include / Exclude specific areas

PWP SM in % v/v FC SM in % v/v Sat. SM in % v/v September PET in cm Sep 17, 2008 RF in mm Sep 17, 2008 SM in % v/v

Agricultural Area Kharif Rice Districts Kharif Coarse Cereal Districts

JUNE 2008JUNE 2009 JUNE 2010 JUNE 2011 Available Soil Moisture (ASM) in % (Rainfall-based Modified Bucket Model) Four-Year Monthly Comparison Colours indicate suitability for Agricultural Operations Colours Red to Yellow (ASM < 50 ): Not suitable for sowing of Crops. Requires irrigation for sowing. Colours Green to Blue: Suitable for Coarse Cereals. Colour Deep Blue: Suitable for Rice. Note: Suitability does not imply sowing of crops which additionally depends on various other factors all of which are reflected in the Crop Calendar of the Region. Not suitable does not imply that no crops are sown as irrigation of the fields is possible.

JUNE 2011JUNE 16-30, 2011 JUNE 26-30, 2011 Soil Moisture Model based Estimation Status as on June 30, 2011 Kharif Rice Area Sown:5.0 L ha (Corresponding Figures for 2010 /2009 /2008/ 2007 : 6.0/ 1.5/ 7.4/ 8.1 L ha) Coarse Cereal Area Sown:7.4 L ha (Corresponding Figures for 2010 /2009 /2008: 11.2/ 3.4/ 12.6 L ha) The problem districts appear in Yellow to Red (ASM < 50%). Gujarat, Saurashtra and Kachchh, Western Rajasthan met-subdivisions are unsuitable for sowing of coarse cereal for entire June. Status of last 15 and 5 day periods show Central Maharashtra, North Karnataka and South Andhra Pradesh are also not suitable for sowing of coarse cereal.

Note: Suitability does not imply sowing of crops which additionally depends on various other factors all of which are reflected in the Crop Calendar of the Region. Not suitable does not imply that no crops are sown as irrigation of the fields is possible. Soil Moisture Model based Estimation (Rainfall-based Modified Bucket Model) Status as on June 30, 2011 Kharif Rice June 16 – 30, 2011 Kharif Coarse Cereal June 16 – 30, 2011

July 01 – 15, 2010 July 01 – 15, 2011 Available Soil Moisture (ASM) in % (Rainfall-based Modified Bucket Model) Four-Year Comparison Colours indicate suitability for Agricultural Operations Colours Red to Yellow (ASM < 50 ): Not suitable for sowing of Crops. Requires irrigation for sowing. Colours Green to Blue: Suitable for Coarse Cereals. Colour Deep Blue: Suitable for Rice. Note: Suitability does not imply sowing of crops which additionally depends on various other factors all of which are reflected in the Crop Calendar of the Region. Not suitable does not imply that no crops are sown as irrigation of the fields is possible. July 01 – 15, 2009 July 01 – 15, 2008

Area Suitable Kharif Rice area July 01 – 15, 2011 Area Suitable Kharif Coarse Cereal area July 01 – 15, 2011 Soil Moisture Model based Estimation Status as on July 15, 2011 Kharif Rice Area Sown: L ha (Corresponding Figures for 2010 /2009 /2008: 116.1/ 135.7/ L ha) Coarse Cereal Area Sown: L ha (Corresponding Figures for 2010 /2009 /2008: 102.7/ 68.7/ 95.3 L ha)

Kharif Rice Area July 18, 2011 Area : L ha July 04 – 18, 2011

Kharif Rice Area Suitable Kharif Rice Area Fallow AUGUST 31, 2009 AUGUST 31, 2008 AUGUST 31, 2010

AUGUST 31, 2009 Coarse Cereal Area Suitable Coarse Cereal Area Fallow AUGUST 31, 2008 AUGUST 31, 2010

The above Soil Moisture Model Acreage is 12% higher than Rainfall-SM estimate to account for Autumn Rice and Irrigated areas Date of Release of SM Acreage : September 02 to 04 of each year

Status as on August 31, 2010: Kharif Rice Area Sown (Rainfed Winter Rice) L ha. (excludes Autumn Rice ~ 40 L ha and Rice Area with irrigation only) Comparison with last two years August 31, 2009 Figure: L ha14.7 % August 31, 2008 Figure: L ha 0.3 % August 31, 2007 Figure: L ha 0.6 % Kharif Coarse Cereal Area Sown L ha. Comparison with last two years August 31, 2009 Figure: L ha 1.6 % August 31, 2008 Figure: L ha -0.3 %

Disclaimers: 1. This all-India early crop forecasting results are output of three models used in sequence: (i)The spatial daily rainfall used in the model is a model-based estimated value using satellite observations of Kalpana VHRR and other satellites and adjusted to IMD ground station observations to remove bias and scaling. (ii)The estimated daily rainfall is the main input to a 1-dimensional soil moisture budgeting model which uses climatic potential evapotranspiration (PET), single set of all-India crop calendar and crop coefficients and representative soil-water holding capacities and hydraulic conductivities for each soil texture category obtained from 1: 6M SOI soil map. This model is used for bunded agricultural fields and does not consider surface runoff to / from the fields. It uses evapotranspiration and deep percolation for the water balance. (iii)The daily soil moisture status expressed as available soil moisture (ASM) in percentage is averaged over 5-day periods and tested for suitability of sowing/transplanting of crops using crop-specific thresholds and convolved with the crop-specific calendar function to forecast the crop area sown till that time. 2. Any irrigation water applied to the fields has not been included as its daily spatial distribution is not available as yet. (However, the model has provision to include it). 3. Area specific crop calendar and crop coefficients have not been used as they are not available. (However, the model has provision to include it). 4. Current/actual PET is not used as it is difficult to compute since it requires more daily weather observations which are not available on time. 5. The crop-specific thresholds for suitability for sowing are experimental and were determined in 2006 season and have been used unchanged for 2007 to 2009 and the current season. 6. Currently, the crop area forecasting is for all-India is available the next day of the date. 7. The current database grid size is approximately 4 x 4 km, suitable for 1: 6M mapping.

RCM RICE AREA 82.1% of Agricultural Area CPC RICE AREA 78.4% of Agricultural Area RCM rainfall : Average RF of CPC rainfall : Average RF of

RCM RICE CALENDAR CPC RICE CALENDAR BLUE – JUN 07 RED – AUG 26 Median Date of Transplanting : June 23 Duration of Sowing (90% of area) : 32 days Median Date of Transplanting : July 01 Duration of Sowing (90% of area) : 43 days RCM rainfall : Average RF of CPC rainfall : Average RF of Histogram of age of Rice Crop Sown as on Aug 31

RCM RICE STRESS DAYS CPC RICE STRESS DAYS Black (for rice area), Red : 0 %Blue : 100 % (Percent No. Days standing crop – Soil Moisture below Field Capacity) RCM rainfall : Average RF of CPC rainfall : Average RF of

MODEL USED: One-dimensional hydrological model (compound “bucket model”) with unsaturated / saturated flow and bunded agricultural fields (20 cm bunds) with overflow has been used to estimate daily soil moisture values in the top 100 cms of soil (root zone). The daily soil moisture model outputs are suitably averaged over past 7-day period of a given date to assess moisture stressed areas. INPUTS: Daily gridded rainfall data over India Climatic Potential Evapo-Transpiration data (Source: Monthly PET data from IMD Agrimet Division, Pune) Survey of India Soil Texture Map – 1:6M Published Moisture Holding Values for each Soil Texture Class, Hydraulic Conductivities