Agricultural Drought Indices - US Department of Agriculture

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mm 140 120 100 80 60 40 20 0 -20 -40 -60 Passo Fundo, RS, Brazil - from July/1990 to June/1991 1990 1991 J1 J2 J3 A1 A2 A3 S1 S2 S3 O1 O2 O3 N1 N2 N3 D1 D2 D3 J1 J2 J3 F1 F2 F3 M1M2M3 A1 A2 A3 M1M2M3 J1 J2 J3 Water Deficiency Water Surplus Water Withdrawal Water Reposition 60 50 1990 Passo Fundo, RS, Brazil - from July/1990 to June/1991 1991 40 mm 30 20 10 SWHC SWS 0 J1 J2 J3 A1 A2 A3 S1 S2 S3 O1 O2 O3 N1 N2 N3 D1 D2 D3 J1 J2 J3 F1 F2 F3 M1 M2 M3 A1 A2 A3 M1 M2 M3 J1 J2 J3 Figure 5. Serial water balance for Passo Fundo, state of Rio Grande do Sul, Brazil, from July 1990 to June 1991, calculated by Thornthwaite and Mather’s model, considering a SWHC of 50 mm. The upper graph is the summary of the water balance, with water surplus and water reposition in the soil (positive values) and water deficiency and water withdrawal (negative values). The lower graph is SWS and its relation to SWHC. Figure 6. Water balance for Argentina, for SWHC = 100 mm, showing conditions from very intense drought (red) to very wet conditions (dark blue). Source: www.smn.gov.ar. 129
Figure 7. Water balance for Brazil, for SWHC = 125 mm. Negative values represent water deficiency and positive values water surplus. Source: www.inmet.gov.br. Figure 8. Percentage of available water in the soil for Uruguay, considering variable SWHC in the different regions of the country. Source: www.inia.org.uy. Another model with a higher degree of complexity is presented by Allen et al. (1998). It is used to determine ET under soil water stress conditions, through the water stress coefficient (Ks), which is responsible for reduction of transpiration depending on the water available in the soil. The ET under soil water stress conditions refers to the ETa, as defined earlier. To estimate ETa, the determination of Ks is required, since ETa = ETP * Kc * Ks, where Ks is estimated by a daily water balance computation for the root zone. Ks is calculated as a function of SWHC, a fraction of SWHC that a crop can extract from the root zone without suffering water stress (p fraction), and root zone depletion (Dr): Ks = (SWHC – Dr) / [(1 - p) * SWHC] (10) Root zone depletion (Dr) is calculated by a daily water balance, with the following components: Dr i = Dr i-1 − (P − RO) i − CR i + ETP i + DP i (11) 130
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Agricultural Drought Indices Procee
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© World Meteorological Organizatio
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Preface With the world population p
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Segura River Basin: Spanish Pilot R
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Table 3. Segura River Basin resourc
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Figure 5. Segura River Basin water
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Drought Indicator Expression After
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Table 5. Analysis of drought impact
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Even with this drought action plan
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that complicates water management b
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Understanding the nature of the haz
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Figure 2. U.S. Drought Monitor for
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Summary Drought is a creeping pheno
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Agricultural Drought—WMO Perspect
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c) CAgM-VI (Washington, USA, 1974)
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an unusually large moisture demand.
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the-clock nature of WIGOS, the anal
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and temporal variations in drought
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Support to Regional Institutions WM
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Williams, M.A.J. and R.C. Balling,
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The day after Black Sunday, an Asso
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Meteorological research at these in
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United States is sent to the Secret
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Palmer Drought Severity Index (PDSI
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PDSI as an operational index since
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WAOB, GIS has become an important t
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USDM as the official criteria for F
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Monitoring Drought Risks in India w
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areas recording large incidences of
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The analysis revealed that out of 1
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Figure 3. Aridity anomaly chart of
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Figure 5. Progression of surface we
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Agricultural Drought Indices in Cur
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Meteorological and Agricultural Dro
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Palmer Drought Severity Index Adapt
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Accumulated WD and WS April 2010 Ac
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Soil Water Storage (SWS) September
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hydrological characteristics, and c
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Agricultural Drought Indices in Cur
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application of drought indices has
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The Value of Crop and Pasture Simul
Page 85 and 86: To assist, many agriculturally-spec
Page 87 and 88: change in Australia. The PDSI provi
Page 89 and 90: Mpelasoka, F.S., M.A. Collier, R. S
Page 91 and 92: supply and demand are fully taken i
Page 93 and 94: In Germany, the Deutsche Wetterdien
Page 95 and 96: creation of a system of European su
Page 97 and 98: The second index is extracted from
Page 99 and 100: Figure 7. Standardized Soil Water I
Page 101 and 102: References Durand, Y., E. Brun, L.
Page 103 and 104: Europe around the Iberian Peninsula
Page 105 and 106: The incoming rainwater and the atmo
Page 107 and 108: Figure 6. Example of SPI map for a
Page 109 and 110: The 1991-95 Drought Episode A long-
Page 111 and 112: adverse climatic impacts on agricul
Page 113 and 114: Agricultural Drought Indices in the
Page 115 and 116: efers to deficiencies in surface an
Page 117 and 118: Figure 5. Time series of standardiz
Page 119 and 120: Limitations of Agricultural Drought
Page 121 and 122: Incorporating a Composite Approach
Page 123 and 124: Figure 3. Daily gridded SPI by regi
Page 125 and 126: The North American Drought Monitor:
Page 127 and 128: process (a) emulates natural cycles
Page 129 and 130: Summary Given the complexity that d
Page 131 and 132: alance models cannot be applied for
Page 133 and 134: 60 50 40 Error 30 20 Systematic Err
Page 135: In Figure 4, examples of the normal
Page 139 and 140: The soil water balance module in th
Page 141 and 142: Water Balance as a Tool for Agricul
Page 143 and 144: Conclusions The topics discussed pr
Page 145 and 146: Use of Crop Models for Drought Anal
Page 147 and 148: The parameters used in crop simulat
Page 149 and 150: a model for cassava and potato (Tsu
Page 151 and 152: ackground. The system’s most impo
Page 153 and 154: management. In research, however, p
Page 155 and 156: Smajstrla, A.G. 1990. Technical Man
Page 157 and 158: Monitoring Regional Drought Conditi
Page 159 and 160: Figure 2 represents the regression
Page 161 and 162: Conclusions and Discussion Several
Page 163 and 164: Experiences During the Drought Peri
Page 165 and 166: During the years 2007 and 2008, for
Page 167 and 168: Figure 6. Management simulation mod
Page 169 and 170: Figure 9. Irrigation diversions in
Page 171 and 172: References Andreu, J., Ferrer Polo,
Page 173 and 174: Table 2. MERIS spectral bands MDS N
Page 175 and 176: Figure 6. Spanish NSDIE during 2008
Page 177 and 178: References Gu, Y., J. F. Brown, J.
Page 179 and 180: Agricultural Drought Indices: Summa
Page 181 and 182: Table 1. Agricultural drought indic
Page 183 and 184: Accumulated Rainfall Deficits In an
Page 185 and 186: Heim (2002) notes that as recently
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each calendar day in the base perio
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The purpose of the climatic charact
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to compare moisture conditions at d
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Table 6. Overview of different drou
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have been adopted because of the av
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TCI = 100 (T max - T) / (T max - T
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Figure 1. The February 8, 2011, US
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8) There is a universal interest in
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Mavromatis, T. 2007. Drought index
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Agricultural Drought Indices - US Department of Agriculture

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